selecting articles for literature review

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• v.9(7); 2013 Jul

Ten Simple Rules for Writing a Literature Review

Marco pautasso.

1 Centre for Functional and Evolutionary Ecology (CEFE), CNRS, Montpellier, France

2 Centre for Biodiversity Synthesis and Analysis (CESAB), FRB, Aix-en-Provence, France

Literature reviews are in great demand in most scientific fields. Their need stems from the ever-increasing output of scientific publications [1] . For example, compared to 1991, in 2008 three, eight, and forty times more papers were indexed in Web of Science on malaria, obesity, and biodiversity, respectively [2] . Given such mountains of papers, scientists cannot be expected to examine in detail every single new paper relevant to their interests [3] . Thus, it is both advantageous and necessary to rely on regular summaries of the recent literature. Although recognition for scientists mainly comes from primary research, timely literature reviews can lead to new synthetic insights and are often widely read [4] . For such summaries to be useful, however, they need to be compiled in a professional way [5] .

When starting from scratch, reviewing the literature can require a titanic amount of work. That is why researchers who have spent their career working on a certain research issue are in a perfect position to review that literature. Some graduate schools are now offering courses in reviewing the literature, given that most research students start their project by producing an overview of what has already been done on their research issue [6] . However, it is likely that most scientists have not thought in detail about how to approach and carry out a literature review.

Reviewing the literature requires the ability to juggle multiple tasks, from finding and evaluating relevant material to synthesising information from various sources, from critical thinking to paraphrasing, evaluating, and citation skills [7] . In this contribution, I share ten simple rules I learned working on about 25 literature reviews as a PhD and postdoctoral student. Ideas and insights also come from discussions with coauthors and colleagues, as well as feedback from reviewers and editors.

Rule 1: Define a Topic and Audience

How to choose which topic to review? There are so many issues in contemporary science that you could spend a lifetime of attending conferences and reading the literature just pondering what to review. On the one hand, if you take several years to choose, several other people may have had the same idea in the meantime. On the other hand, only a well-considered topic is likely to lead to a brilliant literature review [8] . The topic must at least be:

• interesting to you (ideally, you should have come across a series of recent papers related to your line of work that call for a critical summary),
• an important aspect of the field (so that many readers will be interested in the review and there will be enough material to write it), and
• a well-defined issue (otherwise you could potentially include thousands of publications, which would make the review unhelpful).

Ideas for potential reviews may come from papers providing lists of key research questions to be answered [9] , but also from serendipitous moments during desultory reading and discussions. In addition to choosing your topic, you should also select a target audience. In many cases, the topic (e.g., web services in computational biology) will automatically define an audience (e.g., computational biologists), but that same topic may also be of interest to neighbouring fields (e.g., computer science, biology, etc.).

Rule 2: Search and Re-search the Literature

After having chosen your topic and audience, start by checking the literature and downloading relevant papers. Five pieces of advice here:

• keep track of the search items you use (so that your search can be replicated [10] ),
• keep a list of papers whose pdfs you cannot access immediately (so as to retrieve them later with alternative strategies),
• use a paper management system (e.g., Mendeley, Papers, Qiqqa, Sente),
• define early in the process some criteria for exclusion of irrelevant papers (these criteria can then be described in the review to help define its scope), and
• do not just look for research papers in the area you wish to review, but also seek previous reviews.

The chances are high that someone will already have published a literature review ( Figure 1 ), if not exactly on the issue you are planning to tackle, at least on a related topic. If there are already a few or several reviews of the literature on your issue, my advice is not to give up, but to carry on with your own literature review,

The bottom-right situation (many literature reviews but few research papers) is not just a theoretical situation; it applies, for example, to the study of the impacts of climate change on plant diseases, where there appear to be more literature reviews than research studies [33] .

• discussing in your review the approaches, limitations, and conclusions of past reviews,
• trying to find a new angle that has not been covered adequately in the previous reviews, and
• incorporating new material that has inevitably accumulated since their appearance.

When searching the literature for pertinent papers and reviews, the usual rules apply:

• be thorough,
• use different keywords and database sources (e.g., DBLP, Google Scholar, ISI Proceedings, JSTOR Search, Medline, Scopus, Web of Science), and
• look at who has cited past relevant papers and book chapters.

Rule 3: Take Notes While Reading

If you read the papers first, and only afterwards start writing the review, you will need a very good memory to remember who wrote what, and what your impressions and associations were while reading each single paper. My advice is, while reading, to start writing down interesting pieces of information, insights about how to organize the review, and thoughts on what to write. This way, by the time you have read the literature you selected, you will already have a rough draft of the review.

Of course, this draft will still need much rewriting, restructuring, and rethinking to obtain a text with a coherent argument [11] , but you will have avoided the danger posed by staring at a blank document. Be careful when taking notes to use quotation marks if you are provisionally copying verbatim from the literature. It is advisable then to reformulate such quotes with your own words in the final draft. It is important to be careful in noting the references already at this stage, so as to avoid misattributions. Using referencing software from the very beginning of your endeavour will save you time.

Rule 4: Choose the Type of Review You Wish to Write

After having taken notes while reading the literature, you will have a rough idea of the amount of material available for the review. This is probably a good time to decide whether to go for a mini- or a full review. Some journals are now favouring the publication of rather short reviews focusing on the last few years, with a limit on the number of words and citations. A mini-review is not necessarily a minor review: it may well attract more attention from busy readers, although it will inevitably simplify some issues and leave out some relevant material due to space limitations. A full review will have the advantage of more freedom to cover in detail the complexities of a particular scientific development, but may then be left in the pile of the very important papers “to be read” by readers with little time to spare for major monographs.

There is probably a continuum between mini- and full reviews. The same point applies to the dichotomy of descriptive vs. integrative reviews. While descriptive reviews focus on the methodology, findings, and interpretation of each reviewed study, integrative reviews attempt to find common ideas and concepts from the reviewed material [12] . A similar distinction exists between narrative and systematic reviews: while narrative reviews are qualitative, systematic reviews attempt to test a hypothesis based on the published evidence, which is gathered using a predefined protocol to reduce bias [13] , [14] . When systematic reviews analyse quantitative results in a quantitative way, they become meta-analyses. The choice between different review types will have to be made on a case-by-case basis, depending not just on the nature of the material found and the preferences of the target journal(s), but also on the time available to write the review and the number of coauthors [15] .

Rule 5: Keep the Review Focused, but Make It of Broad Interest

Whether your plan is to write a mini- or a full review, it is good advice to keep it focused 16 , 17 . Including material just for the sake of it can easily lead to reviews that are trying to do too many things at once. The need to keep a review focused can be problematic for interdisciplinary reviews, where the aim is to bridge the gap between fields [18] . If you are writing a review on, for example, how epidemiological approaches are used in modelling the spread of ideas, you may be inclined to include material from both parent fields, epidemiology and the study of cultural diffusion. This may be necessary to some extent, but in this case a focused review would only deal in detail with those studies at the interface between epidemiology and the spread of ideas.

While focus is an important feature of a successful review, this requirement has to be balanced with the need to make the review relevant to a broad audience. This square may be circled by discussing the wider implications of the reviewed topic for other disciplines.

Rule 6: Be Critical and Consistent

Reviewing the literature is not stamp collecting. A good review does not just summarize the literature, but discusses it critically, identifies methodological problems, and points out research gaps [19] . After having read a review of the literature, a reader should have a rough idea of:

• the major achievements in the reviewed field,
• the main areas of debate, and
• the outstanding research questions.

It is challenging to achieve a successful review on all these fronts. A solution can be to involve a set of complementary coauthors: some people are excellent at mapping what has been achieved, some others are very good at identifying dark clouds on the horizon, and some have instead a knack at predicting where solutions are going to come from. If your journal club has exactly this sort of team, then you should definitely write a review of the literature! In addition to critical thinking, a literature review needs consistency, for example in the choice of passive vs. active voice and present vs. past tense.

Rule 7: Find a Logical Structure

Like a well-baked cake, a good review has a number of telling features: it is worth the reader's time, timely, systematic, well written, focused, and critical. It also needs a good structure. With reviews, the usual subdivision of research papers into introduction, methods, results, and discussion does not work or is rarely used. However, a general introduction of the context and, toward the end, a recapitulation of the main points covered and take-home messages make sense also in the case of reviews. For systematic reviews, there is a trend towards including information about how the literature was searched (database, keywords, time limits) [20] .

How can you organize the flow of the main body of the review so that the reader will be drawn into and guided through it? It is generally helpful to draw a conceptual scheme of the review, e.g., with mind-mapping techniques. Such diagrams can help recognize a logical way to order and link the various sections of a review [21] . This is the case not just at the writing stage, but also for readers if the diagram is included in the review as a figure. A careful selection of diagrams and figures relevant to the reviewed topic can be very helpful to structure the text too [22] .

Rule 8: Make Use of Feedback

Reviews of the literature are normally peer-reviewed in the same way as research papers, and rightly so [23] . As a rule, incorporating feedback from reviewers greatly helps improve a review draft. Having read the review with a fresh mind, reviewers may spot inaccuracies, inconsistencies, and ambiguities that had not been noticed by the writers due to rereading the typescript too many times. It is however advisable to reread the draft one more time before submission, as a last-minute correction of typos, leaps, and muddled sentences may enable the reviewers to focus on providing advice on the content rather than the form.

Feedback is vital to writing a good review, and should be sought from a variety of colleagues, so as to obtain a diversity of views on the draft. This may lead in some cases to conflicting views on the merits of the paper, and on how to improve it, but such a situation is better than the absence of feedback. A diversity of feedback perspectives on a literature review can help identify where the consensus view stands in the landscape of the current scientific understanding of an issue [24] .

Rule 9: Include Your Own Relevant Research, but Be Objective

In many cases, reviewers of the literature will have published studies relevant to the review they are writing. This could create a conflict of interest: how can reviewers report objectively on their own work [25] ? Some scientists may be overly enthusiastic about what they have published, and thus risk giving too much importance to their own findings in the review. However, bias could also occur in the other direction: some scientists may be unduly dismissive of their own achievements, so that they will tend to downplay their contribution (if any) to a field when reviewing it.

In general, a review of the literature should neither be a public relations brochure nor an exercise in competitive self-denial. If a reviewer is up to the job of producing a well-organized and methodical review, which flows well and provides a service to the readership, then it should be possible to be objective in reviewing one's own relevant findings. In reviews written by multiple authors, this may be achieved by assigning the review of the results of a coauthor to different coauthors.

Rule 10: Be Up-to-Date, but Do Not Forget Older Studies

Given the progressive acceleration in the publication of scientific papers, today's reviews of the literature need awareness not just of the overall direction and achievements of a field of inquiry, but also of the latest studies, so as not to become out-of-date before they have been published. Ideally, a literature review should not identify as a major research gap an issue that has just been addressed in a series of papers in press (the same applies, of course, to older, overlooked studies (“sleeping beauties” [26] )). This implies that literature reviewers would do well to keep an eye on electronic lists of papers in press, given that it can take months before these appear in scientific databases. Some reviews declare that they have scanned the literature up to a certain point in time, but given that peer review can be a rather lengthy process, a full search for newly appeared literature at the revision stage may be worthwhile. Assessing the contribution of papers that have just appeared is particularly challenging, because there is little perspective with which to gauge their significance and impact on further research and society.

Inevitably, new papers on the reviewed topic (including independently written literature reviews) will appear from all quarters after the review has been published, so that there may soon be the need for an updated review. But this is the nature of science [27] – [32] . I wish everybody good luck with writing a review of the literature.

Acknowledgments

Many thanks to M. Barbosa, K. Dehnen-Schmutz, T. Döring, D. Fontaneto, M. Garbelotto, O. Holdenrieder, M. Jeger, D. Lonsdale, A. MacLeod, P. Mills, M. Moslonka-Lefebvre, G. Stancanelli, P. Weisberg, and X. Xu for insights and discussions, and to P. Bourne, T. Matoni, and D. Smith for helpful comments on a previous draft.

Funding Statement

This work was funded by the French Foundation for Research on Biodiversity (FRB) through its Centre for Synthesis and Analysis of Biodiversity data (CESAB), as part of the NETSEED research project. The funders had no role in the preparation of the manuscript.

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• How to Write a Literature Review | Guide, Examples, & Templates

How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates, and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

What is the purpose of a literature review, examples of literature reviews, step 1 – search for relevant literature, step 2 – evaluate and select sources, step 3 – identify themes, debates, and gaps, step 4 – outline your literature review’s structure, step 5 – write your literature review, free lecture slides, other interesting articles, frequently asked questions, introduction.

• Quick Run-through
• Step 1 & 2

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and its scholarly context
• Develop a theoretical framework and methodology for your research
• Position your work in relation to other researchers and theorists
• Show how your research addresses a gap or contributes to a debate
• Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

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Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models, and methods?
• Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

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To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

• Summarize and synthesize: give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: don’t just paraphrase other researchers — add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically evaluate: mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: use transition words and topic sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

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If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

• Sampling methods
• Simple random sampling
• Stratified sampling
• Cluster sampling
• Likert scales
• Reproducibility

 Statistics

• Null hypothesis
• Statistical power
• Probability distribution
• Effect size
• Poisson distribution

Research bias

• Optimism bias
• Cognitive bias
• Implicit bias
• Hawthorne effect
• Anchoring bias
• Explicit bias

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarize yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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How To Find A-Grade Literature For Review

Sourcing, evaluating and organising.

By: David Phair (PhD) and Peter Quella (PhD) | January 2022

As we’ve discussed previously on our blog and YouTube channel, the first step of the literature review process is to source high-quality , relevant resources for your review, and to catalogue these pieces of literature in a systematic way so that you can digest and synthesise all the content efficiently.

In this article, we’ll look discuss 6 important things to keep in mind for the initial stage of your literature review so that you can source high-quality, relevant resources, quickly and efficiently. Let’s get started!

Overview: Literature Review Sourcing

• Develop and follow a clear literature search strategy
• Understand and use different types of literature correctly
• Carefully evaluate the quality of your potential sources
• Use a reference manager and a literature catalogue
• Read as broadly and comprehensively as possible
• Keep your golden thread front of mind throughout the process

1. Have a clear literature search strategy

As with any task in the research process, you need to have a clear plan of action before you get started, or you’ll end up wasting a lot of time and energy. So, before you begin your literature review , it’s useful to develop a simple search strategy . Broadly speaking, a good literature search strategy should include the following steps:

Step one – Clearly identify your golden thread

Your golden thread consists of your research aims , research objectives and research questions . These three components should be tightly aligned to form the focus of your research. If you’re unclear what your research aims and research questions are, you’re not going to have a clear direction when trying to source literature. As a result, you’re going to waste a lot of time reviewing irrelevant resources.

So, make sure that you have clarity regarding your golden thread before you start searching for literature. Of course, your research aims, objectives and questions may evolve or shift as a result of the literature review process (in fact, this is quite common), but you still need to have a clear focus to get things started.

Step two – Develop a keyword/keyphrase list

Once you’ve clearly articulated your golden thread in terms of the research aims, objectives and questions, the next step is to develop a list of keywords or keyphrases, based on these three elements (the golden thread). You’ll also want to include synonyms and alternative spellings (for example, American vs British English) in your list.

For example, if your research aims and research questions involve investigating organisational trust , your keyword list might include:

• Organisational trust
• Organizational trust (US spelling)
• Consumer trust
• Brand trust
• Online trust

When it comes to brainstorming keywords, the more the better . Don’t hold back at this stage. You’ll quickly find out which ones are useful, and which aren’t when you start searching. So, it’s best to just go as broad as possible here to ensure you cast a wide net.

Step three – Identify the relevant databases

Now that you’ve got a comprehensive set of keywords, the next step is to identify which literature databases will be most useful and relevant for your particular study. There are hundreds, if not thousands of databases out there, and they are often subject or discipline-specific . For example, within the medicine space, Medline is a popular one.

To identify relevant databases, it’s best to speak to your research advisor/supervisor, Grad Coach or a librarian at your university library. Oftentimes, a quick chat with a skilled librarian can yield tremendous insight. Don’t be shy to ask – chances are, they’ll be thrilled that you asked!

At this stage, you might be asking, “why not just use Google Scholar?”. Of course, an academic search engine like Google Scholar will be useful in terms of getting started and finding a broad range of resources, but it won’t always present every possible resource  or the best quality resources. It also has limited filtering options compared to some of the specialist databases, so you shouldn’t rely purely on Google Scholar.

Step four – Use Boolean operators to refine your search

Once you’ve identified your keywords and databases, it’s time to start searching for literature – hooray! However, you’ll quickly find that there is a seemingly endless number of journal articles to sift through, and you have limited time to work through the literature. So, you’ll need to get smart about how you use these databases – enter Boolean operators.

Boolean operators are special characters that allow you to refine your search. Common operators include:

• AND – only show results that contain both X and Y
• OR – show results that contain X or Y
• NOT – show results that include X, but not Y

These operators are incredibly useful, especially when there are topics that are very similar to yours but are not relevant . For example, if you’re researching something about the growth of apples, you’ll want to exclude all literature related to Apple, the company. Boolean operators allow you to cut out the irrelevant content and improve the signal to noise ratio in your search.

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2. Use different types of literature correctly

Once you start searching for literature, you’ll quickly notice that there are different “types” of resources that come up. It’s important to understand the different types of literature available to you and how to use each of them appropriately.

Generally speaking, you’ll find three categories of literature:

Primary literature

Secondary literature

Tertiary literature

Primary literature refers to journal articles , typically peer reviewed, which document a study that was undertaken, where data were collected and analysed, and findings were discussed. For example, a journal article that involves the collection and analysis of survey data to identify differences in personality between two groups of people.

Primary literature should, ideally, form the foundation of your literature review – the bread and butter, so to speak. You’ll likely refer to many of the arguments made and findings identified in these types of articles to build your own arguments throughout your literature review. You’ll also rely on these types of articles for theoretical models and frameworks, which may form the foundation of your own proposed framework, depending on the nature of your research.

Lastly, primary literature can be a useful source of measurement scales for quantitative studies. For example, many journal articles will include a copy of the survey measures they used at the end of the article, which will typically be reliable and valid. You can either use these “as is” or as a foundation for your own survey measures .

So, long story short, you’ll need a good stockpile of these types of resources. They are, admittedly, more “dense” and challenging to digest than the other types of literature, but taking the time to work through them will pay off greatly.

Secondary literature refers to journal articles that summarise and integrate the findings from primary literature. For example, you’ll likely find “review of the literature” type journal articles which provide an overview of the current state of the research (at the time of publication, of course).

Secondary literature is very useful for orienting yourself with regards to the current state of knowledge and identifying key researchers , seminal works and so on. In other words, they’re a good tool to make sure you’ve got a broad, comprehensive view of what all is out there. They’re not going to give you the level of detail that primary literature will (and they’ll likely be a bit outdated), but they’ll point you in the right direction.

In practical terms, it’s a good idea to start by reviewing secondary literature-type articles to help you get a bird’s eye view of the landscape and then dive deeper into the primary literature to get a grasp of the specifics and to bring your knowledge up to date with the most current studies.

The final category of literature refers to sources that would be considered less academic and scientifically rigorous in nature, but up to date and highly relevant. For example, sources such as current industry and country reports published by management consulting groups, news articles, blog posts and so on.

While these sources are not as credible and trustworthy as journal articles (especially peer-reviewed ones), they can provide very up to date information , whereas academic research tends to roll out quite slowly. Therefore, they can be very useful for contextualising your research topic and/or demonstrating a current trend. Quite often, you’d cite these types of sources in your introduction chapter rather than your literature review chapter, but you may still have use for them in the latter.

In summary, it’s important to understand the three different types of literature – primary, secondary and tertiary, and use them appropriately in your dissertation, thesis or research project.

3. Carefully evaluate the quality of your sources

As we’ve alluded to, not all literature is created equally. Not only does literature vary in terms of type (i.e., primary vs secondary), it also varies in terms of overall quality .

Simply put, all sources exist on a quality spectrum . On the high end of the spectrum are peer-reviewed articles published in popular, credible journals. Next are journal articles that are not peer-reviewed, or that are published in lower quality or lesser-known journals. In the middle are sources like textbooks and reports by professional organisations (e.g., management consulting firms). On the low end are sources like newspapers, blog posts and social media posts.

As you can probably see, this loosely reflects the categories we mentioned previously (primary, secondary and tertiary literature), so there is once again a trade-off between quality and recency . Therefore, you need to carefully evaluate the quality of each potential source and let this inform how you use it in your literature review. Importantly, this doesn’t mean that you can’t include a newspaper article or blog post as a source – it just means that you shouldn’t rely too heavily on these types of courses as the core of your argument.

When evaluating journal articles, you can consider their citation count (i.e., the number of other articles that reference them) as a quality indicator. But keep in mind that citation count is a product of many factors , including the popularity of the article, the popularity of the research field and most importantly, time. In other words, it’s natural for newer articles to have lower citation counts. This is useful to keep in mind, as you ideally want to focus on more recent literature (published within the last 3-5 years) in your literature review.

In summary, aim to focus on higher-quality literature , especially when you’re building core arguments in your literature review. You don’t, for example, want to make an argument regarding the importance and novelty of your research (i.e., its justification) based on some blogger’s opinion.

4. Use a reference manager and literature catalogue

As you review the literature and build your collection of potential sources, you’ll need a way to stay on top of all the details. To this end, it’s essential that you make use of both a reference manager and a literature catalogue . Let’s take a look at each of these.

The reference manager

Reference management software helps you store the reference information for each of your articles and manages the citation and reference list building task as you write up your actual literature review chapter. In other words, a reference manager ensures that your citations and reference list are correctly formatted in the reference style required by your university – e.g., Harvard, APA , MLA, etc.

Using a reference manager saves you the hassle of trying to manually type out your in-text citations and reference list, which you’re bound to mess up in some way. A simple comma out of place, incorrect italicisation or boldfacing can result in you losing marks, and that’s highly likely when you’re dealing with a large number of references. So, it just makes sense to use a piece of software for this task.

The good news is that there are loads of options , many of which are free . For new researchers, we usually recommend Mendeley or Zotero . So, don’t waste your time trying to manage your references manually – get yourself a reference manager ASAP.

The literature catalogue

The second tool you’ll need is a literature catalogue. This is simply an Excel document that you can easily compile yourself (or download our free one here ), where you list and categorise all your literature. You might doubt whether it’s really necessary to have a separate catalogue when you’ve already logged your reference data in a reference manager, but trust us, you’re going to need it. It’s quite common that throughout the literature review process, you’ll review hundreds of articles , so it’s simply impossible that you’ll remember all the details.

What makes a literature catalogue extremely powerful is that you can store as much information as you want for each piece of literature that you include (whereas a reference manager only includes basic fields). Typically, you would include things like:

• Title of the article
• One-line summary of the research
• Key findings and takeaways
• Context (i.e. where did it take place)
• Useful quotes
• Methodology (e.g. qualitative, quantitative or mixed methods)
• Category (you can customise as many categories as makes sense for you)
• Quality of resource
• Type of literature (e.g. primary, secondary or tertiary)

These are just some examples – ultimately you need to customise your catalogue to suit your needs. But, as you can see, the more detailed you get, the more useful your catalogue will become when it’s time to synthesise the research and write up your literature. For example, you could quickly filter the catalogue to display all papers that support a certain hypothesis, that argue in a specific direction, or that were written at a certain time.

5. Read widely (and efficiently)

As we’ve discussed in other posts , the purpose of the literature review chapter is to present and synthesise the current state of knowledge in relation to your research aims, objectives and research questions. To do this, you’ll need to read as broadly and comprehensively as possible. You’ll need to demonstrate to your marker that you “know your stuff” and have a strong understanding of the relevant literature.

Ideally, your literature review should include an eclectic mix of research that features multiple perspectives . In other words, you need to avoid getting tunnel vision and running down one narrow stream of literature. Ideally, you want to highlight both the agreements and disagreements in the literature to show that you’ve got a well-balanced view of the situation.

If your topic is particularly novel and there isn’t a lot of literature available, you can focus your efforts on adjacent literature . For example, if you’re researching factors that cultivate organisational trust in Germany, but there’s very little literature on this, you can draw on US and UK-based studies to form your theoretical foundation. Similarly, if you’re investigating an occurrence in an under-researched industry, you can look at other industries for literature.

As you read each journal article, be sure to scan the reference list for further reading (this technique is called “snowballing”). By doing this, you will quickly identify key literature within a topic area and fast-track your literature review process. You can also check which articles have cited any given article using Google Scholar, which will give you a “forward view” in terms of the progress of the literature.

Given that you’ll need to work through a large amount of literature, it’s useful to adopt a “strategic skimming ” approach when you’re initially assessing articles, so that you don’t need to read the entire journal article . In practical terms, this means you can focus on just the title and abstract at first, and if the article seems relevant based on those, you can jump to the findings section and limitations section. These sections will give you a solid indicator as to whether the resource is relevant to your study, which you can then shortlist for full reading.

6. Keep your golden thread front of mind

Your golden thread (i.e., your research aims, objectives and research questions) needs to guide every decision you make throughout your dissertation, thesis, or research project. This is especially true in the literature review stage, as the golden thread should act as a litmus test for relevance whenever you’re reviewing potential articles or resources. In other words, if an article doesn’t relate to your golden thread, its probably not worth spending time on.

Keep in mind that your research aims, objectives and research questions may evolve as a result of the literature review process. For example, you may find that after reviewing the literature in more depth, your topic focus is not as novel as you originally thought, or that there’s an adjacent area that is more deserving of investigation. This is perfectly natural, so don’t be surprised if your focus shifts somewhat during the review process. Just remember to update your literature review in this case and be sure to update any previous chapters so that your document has a consistent focus throughout.

Wrapping up

In this article, we covered 6 pointers to help you find and evaluate high-quality resources for your literature review. To recap:

• Understand and use different types of literature for the right purpose

If you have any questions, please feel free to leave a comment . Alternatively, if you’d like hands-on help with your literature review, be sure to check out our 1-on-1 private coaching services here.

Psst… there’s more!

This post is an extract from our bestselling Udemy Course, Literature Review Bootcamp . If you want to work smart, you don't want to miss this .

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this is very helpful to any researcher, I am learning this for the benefit of myself and overs as a library staff

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How To Write A Literature Review - A Complete Guide

Table of Contents

A literature review is much more than just another section in your research paper. It forms the very foundation of your research. It is a formal piece of writing where you analyze the existing theoretical framework, principles, and assumptions and use that as a base to shape your approach to the research question.

Curating and drafting a solid literature review section not only lends more credibility to your research paper but also makes your research tighter and better focused. But, writing literature reviews is a difficult task. It requires extensive reading, plus you have to consider market trends and technological and political changes, which tend to change in the blink of an eye.

Now streamline your literature review process with the help of SciSpace Copilot. With this AI research assistant, you can efficiently synthesize and analyze a vast amount of information, identify key themes and trends, and uncover gaps in the existing research. Get real-time explanations, summaries, and answers to your questions for the paper you're reviewing, making navigating and understanding the complex literature landscape easier.

In this comprehensive guide, we will explore everything from the definition of a literature review, its appropriate length, various types of literature reviews, and how to write one.

What is a literature review?

A literature review is a collation of survey, research, critical evaluation, and assessment of the existing literature in a preferred domain.

Eminent researcher and academic Arlene Fink, in her book Conducting Research Literature Reviews , defines it as the following:

“A literature review surveys books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated.

Literature reviews are designed to provide an overview of sources you have explored while researching a particular topic, and to demonstrate to your readers how your research fits within a larger field of study.”

Simply put, a literature review can be defined as a critical discussion of relevant pre-existing research around your research question and carving out a definitive place for your study in the existing body of knowledge. Literature reviews can be presented in multiple ways: a section of an article, the whole research paper itself, or a chapter of your thesis.

A literature review does function as a summary of sources, but it also allows you to analyze further, interpret, and examine the stated theories, methods, viewpoints, and, of course, the gaps in the existing content.

As an author, you can discuss and interpret the research question and its various aspects and debate your adopted methods to support the claim.

What is the purpose of a literature review?

A literature review is meant to help your readers understand the relevance of your research question and where it fits within the existing body of knowledge. As a researcher, you should use it to set the context, build your argument, and establish the need for your study.

What is the importance of a literature review?

The literature review is a critical part of research papers because it helps you:

• Gain an in-depth understanding of your research question and the surrounding area
• Convey that you have a thorough understanding of your research area and are up-to-date with the latest changes and advancements
• Establish how your research is connected or builds on the existing body of knowledge and how it could contribute to further research
• Elaborate on the validity and suitability of your theoretical framework and research methodology
• Identify and highlight gaps and shortcomings in the existing body of knowledge and how things need to change
• Convey to readers how your study is different or how it contributes to the research area

How long should a literature review be?

Ideally, the literature review should take up 15%-40% of the total length of your manuscript. So, if you have a 10,000-word research paper, the minimum word count could be 1500.

Your literature review format depends heavily on the kind of manuscript you are writing — an entire chapter in case of doctoral theses, a part of the introductory section in a research article, to a full-fledged review article that examines the previously published research on a topic.

Another determining factor is the type of research you are doing. The literature review section tends to be longer for secondary research projects than primary research projects.

What are the different types of literature reviews?

All literature reviews are not the same. There are a variety of possible approaches that you can take. It all depends on the type of research you are pursuing.

Here are the different types of literature reviews:

Argumentative review

It is called an argumentative review when you carefully present literature that only supports or counters a specific argument or premise to establish a viewpoint.

Integrative review

It is a type of literature review focused on building a comprehensive understanding of a topic by combining available theoretical frameworks and empirical evidence.

Methodological review

This approach delves into the ''how'' and the ''what" of the research question —  you cannot look at the outcome in isolation; you should also review the methodology used.

Systematic review

This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research and collect, report, and analyze data from the studies included in the review.

Meta-analysis review

Meta-analysis uses statistical methods to summarize the results of independent studies. By combining information from all relevant studies, meta-analysis can provide more precise estimates of the effects than those derived from the individual studies included within a review.

Historical review

Historical literature reviews focus on examining research throughout a period, often starting with the first time an issue, concept, theory, or phenomenon emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and identify future research's likely directions.

Theoretical Review

This form aims to examine the corpus of theory accumulated regarding an issue, concept, theory, and phenomenon. The theoretical literature review helps to establish what theories exist, the relationships between them, the degree the existing approaches have been investigated, and to develop new hypotheses to be tested.

Scoping Review

The Scoping Review is often used at the beginning of an article, dissertation, or research proposal. It is conducted before the research to highlight gaps in the existing body of knowledge and explains why the project should be greenlit.

State-of-the-Art Review

The State-of-the-Art review is conducted periodically, focusing on the most recent research. It describes what is currently known, understood, or agreed upon regarding the research topic and highlights where there are still disagreements.

Can you use the first person in a literature review?

When writing literature reviews, you should avoid the usage of first-person pronouns. It means that instead of "I argue that" or "we argue that," the appropriate expression would be "this research paper argues that."

Do you need an abstract for a literature review?

Ideally, yes. It is always good to have a condensed summary that is self-contained and independent of the rest of your review. As for how to draft one, you can follow the same fundamental idea when preparing an abstract for a literature review. It should also include:

• The research topic and your motivation behind selecting it
• A one-sentence thesis statement
• An explanation of the kinds of literature featured in the review
• Summary of what you've learned
• Conclusions you drew from the literature you reviewed
• Potential implications and future scope for research

Here's an example of the abstract of a literature review

Is a literature review written in the past tense?

Yes, the literature review should ideally be written in the past tense. You should not use the present or future tense when writing one. The exceptions are when you have statements describing events that happened earlier than the literature you are reviewing or events that are currently occurring; then, you can use the past perfect or present perfect tenses.

How many sources for a literature review?

There are multiple approaches to deciding how many sources to include in a literature review section. The first approach would be to look level you are at as a researcher. For instance, a doctoral thesis might need 60+ sources. In contrast, you might only need to refer to 5-15 sources at the undergraduate level.

The second approach is based on the kind of literature review you are doing — whether it is merely a chapter of your paper or if it is a self-contained paper in itself. When it is just a chapter, sources should equal the total number of pages in your article's body. In the second scenario, you need at least three times as many sources as there are pages in your work.

Quick tips on how to write a literature review

To know how to write a literature review, you must clearly understand its impact and role in establishing your work as substantive research material.

You need to follow the below-mentioned steps, to write a literature review:

• Outline the purpose behind the literature review
• Search relevant literature
• Examine and assess the relevant resources
• Discover connections by drawing deep insights from the resources
• Structure planning to write a good literature review

1. Outline and identify the purpose of  a literature review

As a first step on how to write a literature review, you must know what the research question or topic is and what shape you want your literature review to take. Ensure you understand the research topic inside out, or else seek clarifications. You must be able to the answer below questions before you start:

• How many sources do I need to include?
• What kind of sources should I analyze?
• How much should I critically evaluate each source?
• Should I summarize, synthesize or offer a critique of the sources?
• Do I need to include any background information or definitions?

Additionally, you should know that the narrower your research topic is, the swifter it will be for you to restrict the number of sources to be analyzed.

2. Search relevant literature

Dig deeper into search engines to discover what has already been published around your chosen topic. Make sure you thoroughly go through appropriate reference sources like books, reports, journal articles, government docs, and web-based resources.

You must prepare a list of keywords and their different variations. You can start your search from any library’s catalog, provided you are an active member of that institution. The exact keywords can be extended to widen your research over other databases and academic search engines like:

• Google Scholar
• Microsoft Academic
• Science.gov

Besides, it is not advisable to go through every resource word by word. Alternatively, what you can do is you can start by reading the abstract and then decide whether that source is relevant to your research or not.

Additionally, you must spend surplus time assessing the quality and relevance of resources. It would help if you tried preparing a list of citations to ensure that there lies no repetition of authors, publications, or articles in the literature review.

3. Examine and assess the sources

It is nearly impossible for you to go through every detail in the research article. So rather than trying to fetch every detail, you have to analyze and decide which research sources resemble closest and appear relevant to your chosen domain.

While analyzing the sources, you should look to find out answers to questions like:

• What question or problem has the author been describing and debating?
• What is the definition of critical aspects?
• How well the theories, approach, and methodology have been explained?
• Whether the research theory used some conventional or new innovative approach?
• How relevant are the key findings of the work?
• In what ways does it relate to other sources on the same topic?
• What challenges does this research paper pose to the existing theory
• What are the possible contributions or benefits it adds to the subject domain?

Be always mindful that you refer only to credible and authentic resources. It would be best if you always take references from different publications to validate your theory.

Always keep track of important information or data you can present in your literature review right from the beginning. It will help steer your path from any threats of plagiarism and also make it easier to curate an annotated bibliography or reference section.

4. Discover connections

At this stage, you must start deciding on the argument and structure of your literature review. To accomplish this, you must discover and identify the relations and connections between various resources while drafting your abstract.

A few aspects that you should be aware of while writing a literature review include:

• Rise to prominence: Theories and methods that have gained reputation and supporters over time.
• Constant scrutiny: Concepts or theories that repeatedly went under examination.
• Contradictions and conflicts: Theories, both the supporting and the contradictory ones, for the research topic.
• Knowledge gaps: What exactly does it fail to address, and how to bridge them with further research?
• Influential resources: Significant research projects available that have been upheld as milestones or perhaps, something that can modify the current trends

Once you join the dots between various past research works, it will be easier for you to draw a conclusion and identify your contribution to the existing knowledge base.

5. Structure planning to write a good literature review

There exist different ways towards planning and executing the structure of a literature review. The format of a literature review varies and depends upon the length of the research.

Like any other research paper, the literature review format must contain three sections: introduction, body, and conclusion. The goals and objectives of the research question determine what goes inside these three sections.

Nevertheless, a good literature review can be structured according to the chronological, thematic, methodological, or theoretical framework approach.

Literature review samples

1. Standalone

2. As a section of a research paper

How SciSpace Discover makes literature review a breeze?

SciSpace Discover is a one-stop solution to do an effective literature search and get barrier-free access to scientific knowledge. It is an excellent repository where you can find millions of only peer-reviewed articles and full-text PDF files. Here’s more on how you can use it:

Find the right information

Find what you want quickly and easily with comprehensive search filters that let you narrow down papers according to PDF availability, year of publishing, document type, and affiliated institution. Moreover, you can sort the results based on the publishing date, citation count, and relevance.

Assess credibility of papers quickly

When doing the literature review, it is critical to establish the quality of your sources. They form the foundation of your research. SciSpace Discover helps you assess the quality of a source by providing an overview of its references, citations, and performance metrics.

Get the complete picture in no time

SciSpace Discover’s personalized suggestion engine helps you stay on course and get the complete picture of the topic from one place. Every time you visit an article page, it provides you links to related papers. Besides that, it helps you understand what’s trending, who are the top authors, and who are the leading publishers on a topic.

Make referring sources super easy

To ensure you don't lose track of your sources, you must start noting down your references when doing the literature review. SciSpace Discover makes this step effortless. Click the 'cite' button on an article page, and you will receive preloaded citation text in multiple styles — all you've to do is copy-paste it into your manuscript.

Final tips on how to write a literature review

A massive chunk of time and effort is required to write a good literature review. But, if you go about it systematically, you'll be able to save a ton of time and build a solid foundation for your research.

We hope this guide has helped you answer several key questions you have about writing literature reviews.

Would you like to explore SciSpace Discover and kick off your literature search right away? You can get started here .

Frequently Asked Questions (FAQs)

1. how to start a literature review.

• What questions do you want to answer?

• What sources do you need to answer these questions?

• What information do these sources contain?

• How can you use this information to answer your questions?

2. What to include in a literature review?

• A brief background of the problem or issue

• What has previously been done to address the problem or issue

• A description of what you will do in your project

• How this study will contribute to research on the subject

3. Why literature review is important?

The literature review is an important part of any research project because it allows the writer to look at previous studies on a topic and determine existing gaps in the literature, as well as what has already been done. It will also help them to choose the most appropriate method for their own study.

4. How to cite a literature review in APA format?

To cite a literature review in APA style, you need to provide the author's name, the title of the article, and the year of publication. For example: Patel, A. B., & Stokes, G. S. (2012). The relationship between personality and intelligence: A meta-analysis of longitudinal research. Personality and Individual Differences, 53(1), 16-21

5. What are the components of a literature review?

• A brief introduction to the topic, including its background and context. The introduction should also include a rationale for why the study is being conducted and what it will accomplish.

• A description of the methodologies used in the study. This can include information about data collection methods, sample size, and statistical analyses.

• A presentation of the findings in an organized format that helps readers follow along with the author's conclusions.

6. What are common errors in writing literature review?

• Not spending enough time to critically evaluate the relevance of resources, observations and conclusions.

• Totally relying on secondary data while ignoring primary data.

• Letting your personal bias seep into your interpretation of existing literature.

• No detailed explanation of the procedure to discover and identify an appropriate literature review.

7. What are the 5 C's of writing literature review?

• Cite - the sources you utilized and referenced in your research.

• Compare - existing arguments, hypotheses, methodologies, and conclusions found in the knowledge base.

• Contrast - the arguments, topics, methodologies, approaches, and disputes that may be found in the literature.

• Critique - the literature and describe the ideas and opinions you find more convincing and why.

• Connect - the various studies you reviewed in your research.

8. How many sources should a literature review have?

When it is just a chapter, sources should equal the total number of pages in your article's body. if it is a self-contained paper in itself, you need at least three times as many sources as there are pages in your work.

9. Can literature review have diagrams?

• To represent an abstract idea or concept

• To explain the steps of a process or procedure

• To help readers understand the relationships between different concepts

10. How old should sources be in a literature review?

Sources for a literature review should be as current as possible or not older than ten years. The only exception to this rule is if you are reviewing a historical topic and need to use older sources.

11. What are the types of literature review?

• Argumentative review

• Integrative review

• Methodological review

• Systematic review

• Meta-analysis review

• Historical review

• Theoretical review

• Scoping review

• State-of-the-Art review

12. Is a literature review mandatory?

Yes. Literature review is a mandatory part of any research project. It is a critical step in the process that allows you to establish the scope of your research, and provide a background for the rest of your work.

But before you go,

• Six Online Tools for Easy Literature Review
• Evaluating literature review: systematic vs. scoping reviews
• Systematic Approaches to a Successful Literature Review
• Writing Integrative Literature Reviews: Guidelines and Examples

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Useful Tool to Develop your Topic

Watch this video about Concept Mapping to become a Research Pro!

• Mind Mapping (also known as Concept Mapping) A helpful handout to show step by step how to create a concept map to map out a topic.

The Research Process

Planning : Before searching for articles or books, brainstorm to develop keywords that best describe your research question.

Searching : While searching take note of what other keywords are used to describe your topic  and use them to do more searches

     ♠ Most articles include a keyword section

     ♠ Key concepts names may change through time so make sure to check for variations

Organizing : Start organizing your results by categories/key concepts or any organizing principle that make sense for you. This will help you later when you are ready to analyze your findings

Analyzing : While reading, start making notes of key concepts and commonalities and disagreement among the research articles you find.

♠ Create a spreadsheet document to record what articles you are finding useful and why.

♠ Create fields to write summaries of articles or quotes for future citing and paraphrasing .

Writing : Synthesize your findings. Use your own voice to explain to your readers what you learned about the literature your search; its weaknesses and strengths; what is missing or ignored

Repeat : at any given time of the process you can go back to a previous step as necessary

Advanced Searching

• Boolean Searching (AND, OR, NOT): Words that help you connect your terms in a logical way for the system understand you 
• Proximity Searching (N/# or W/#): It allows you to search for two or more words that occur within a specified number of words (or fewer) of each other in the databases.
• Limiters/Filters : These are options available on the advanced page to let you control what type of document you want to search (articles), dates, language, peer-review, etc...
• Question mark (?) or a pound sign (#) for wildcard: useful when you don't know how something is spelled out, e.g. if you are looking about articles about color, if you want to find articles with the spelling colour (British English), you can use colo?r to find either spelling.
• Asterisk (*) for truncation: useful for getting results with keywords with multiple endings, e.g. comput* for computer, computers, computing , etc.
• UC Library Search Explained! Check the Search tips to better used our library catalog and articles search system
• EBSCOhost Searching Tips An useful guide about how to best search EBSCOhost databases
• ProQuest Database Search Tips An useful guide about how to best search ProQuest databases
• Are you working on an emerging topic? You are not likely to find many sources, which is good because you are trying to prove that this is a topic that needs more research. But, it is not enough to say that you found few or no articles on your topic in your field. You need to look broadly to other disciplines (also known as triangulation ) to see if your research topic has been studied from other perspectives as a way to validate the uniqueness of your research question.
• Are you working on something that has been studied extensively? Then you are going to find many sources and you will want to limit how far you want to look back. Use limiters to eliminate research that may be dated and opt to search for resources published within the last 5-10 years.
• Want to keep track of your searches , send alerts to your email when new articles in your topic are available? Create an account in any of our databases!

Following the Citation Trail!

Many databases today have special featured that show you how many times an article was cited by and by who and offer you links to those articles.

See below some recommended resources:

• Google Scholar This link opens in a new window Google Scholar not only helps you find articles on your topic, but it also offers (when available) a link called Cited by that tells you how many times the articles have been cited in their system (numbers varied depending on databases). You can click the link to see the list and access the full text of the articles (if available). Click the "Get it at UC" link to check for full text. more... less... Materials Indexed: Artworks; Audio; Biographical Information; Book Chapters; Book Reviews; Books; Business Data; Charts & Graphs; Conference Proceedings; Economic Data; Essays; Financial Data; Government Documents; Images; Journal Articles; Legal Literature; Lyrics; Magazine Articles; Maps; Monologues; Music Recordings; Musical Scores; Newsletter Articles; Newspaper Articles; Pamphlets; Patents & Trademarks; Photographs; Plays; Poetry; Poster Sessions; Preprints; Primary Sources; Prose; Public Opinion Polls; Questionnaire Responses; Radio Broadcasts; Reports; Statistics; Technical Data; Technical Reports; Television Broadcasts; Theses & Dissertations; Video
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Write a Literature Review

• Developing a Research Question
• Database Searching
• Documenting Your Search and Findings
• Discipline-Specific Literature Reviews

Why should I document my search?

Documenting searches for traditional literature reviews is not essential but will help you stay organized and perhaps save you some time. Documenting your search can help you:

• keep track of what you've done so that you don't repeat unproductive searches
• reuse successful search strategies for future papers

Consider whether it makes sense for you to document the following during your search process:

• the databases and resources used
• search strategies for each resource, including the search terms and limits used (e.g. dates, language, etc.)
• the number of results for each search strategy

Selecting Articles for Your Literature Review

You may want to think about criteria that will be used to select articles for your literature review based on your research question.  These are commonly known as inclusion criteria and exclusion criteria. Inclusion criteria are the elements of an article that must be present in order for it to be eligible for inclusion in a literature review, while exclusion criteria are the elements of an article that disqualify the study from inclusion in a literature review.

For example:

• Must certain methodologies be used?
• Should the studies have been published in the last 5 years?

Consider Using a Synthesis Matrix

As you read, you'll encounter various ideas, disagreements, methods, and perspectives which can be hard to organize in a meaningful way. Because you'll be reading a number of resources, a synthesis matrix helps you record the main points of each source and document how sources relate to each other.

• Download Excel Synthesis Matrix Feel free to customize columns to your needs.

What is Reference Management?

Reference management is when you use specific tools to help you organize the references you find during a lit review search. Citation Management Software, like Zotero or Mendeley, are commonly used in literature reviews. VCU Libraries has more information about Choosing a Citation Tool  to fit your needs.

Need Help Writing the Literature Review?

Now that you have conducted your research and documented your findings, you're ready to begin writing your literature review.   VCU's Writing Center consultants can help you plan, develop, and organize your literature review and a follow-up appointment will help you edit, proofread, and revise it.

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Literature Review Basics and Searching Skills

• Selecting Criteria
• Getting Started
• Developing Research Questions
• Selecting Databases
• Searching Databases
• Documenting Searches
• Organizing Findings
• Managing Citations & References
• Submitting Your Manuscript
• Finding Help

Selection Criteria

You may want to think about criteria that will be used to select articles for your literature review based on your research question. These are commonly known as  inclusion criteria  and  exclusion criteria . Be aware that you may introduce bias into the final review if these are not used thoughtfully.

Inclusion Criteria

Inclusion criteria are the elements of an article that must be present in order for it to be eligible for inclusion in a literature review.  Some examples are:

• Included studies must have compared certain treatments
• Included studies must be experimental
• Included studies must have been published in the last 5 years

Exclusion Criteria

Exclusion criteria are the elements of an article that disqualify the study from inclusion in a literature review.  Some examples are:

• Study used an observational design
• Study used a qualitative methodology
• Study was published more than 5 years ago
• Study was published in a language other than English
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Systematic and systematic-like review toolkit: Step 3: Screening and selection of articles

Systematic and systematic-like review toolkit.

• Systematic and systematic-like reviews overview
• Step 1: Formulating the research question
• Step 2: Developing the search
• Step 3: Screening and selection of articles
• Step 4: Appraisal of articles
• Step 5: Writing and publishing
• Filters and complex search examples
• Evidence synthesis support services

Tip: Look for these icons for guidance on which technique is required

Email your Librarians

Step 3: Screening tools

Screening is the process of identifying studies from the literature search for inclusion in the review.

PRISMA  (Preferred Reporting Items for Systematic reviews and Meta-Analyses) is fast becoming a standard for reporting of systematic reviews and meta-analyses, but is also used with other review types.

It includes a procedural checklist, and a flow diagram to illustrate the screening process.

Tools to manage the screening process

Consider using one of the tools below to manage the screening process.

• EndNote  (Deakin supported)  Export searches to an EndNote library.  Create groups to screen citations against inclusion and exclusion criteria, then populate the PRISMA flow diagram.
• Covidence  (Deakin supported) Cochrane-recommended web-based software that streamlines the production of systematic reviews. Allows importing of citations, management of screening by multiple reviewers, data extraction and data export.  Deakin has a license for Covidence and for more information go to the Covidence page .
• Rayyan  (free) Web based collaborative application facilitates team screening, including the upload of citations and  recording of the decisions behind the screening process. A mobile app allows you to screening articles any place. Read the Rayyan for Systematic Reviews guide for further advice on this tool. When exporting from EndNote, choose the RIS format to import into Rayyan.  More instructions are in this EndNote guide .

When working with Deakin subscribed material (for example, PDFs of journal articles), please ensure that you comply with all licences, terms and conditions.  This applies to all screening and reference management tools, particularly when storing copies of articles.  Articles cannot be shared with non-Deakin staff or students.

The screening process

Your review protocol developed at the beginning of your review will have outlined inclusion and exclusion criteria.  These will form the basis of the screening process.

Begin by screening titles and abstracts to remove obviously irrelevant material. At this stage you may not need to provide justification for your exclusions.

You will then need to examine the full text of an article for more detailed screening against your eligibility criteria. At this stage you must provide reasons why you exclude documents.

• appropriate study population (age, geography, illness)
• appropriate intervention/method/measurements
• comparable environment/ population 
• language - can the article be sourced/translated in the language required?

When reviewing the full text of the article, consider:

• appropriate method/measurement
• appropriate sample size
• duplication of data  (avoid counting the same data twice)
• access to data not included in the article if required

Using review teams to reduce selection bias

A team of at least two or three reviewers is important for the screening process to reduce the risk of selection errors and selection bias.

Reviewer teams should:

• have a good knowledge of the topic for fast and accurate screening
• prepare for screening by doing a pilot screen to establish themes or possible difficulties          
• work independently during the screening process to avoid influencing other's decisions

The review paper should detail how many reviewers screened and the process used for resolving any disagreement.

Discover more

• Implementation of the selection process
• Selection of reviews
• Who should extract data?
• Joanna Briggs Institute Manual for Evidence Synthesis
• Systematic reviews: CRD’s guidance for undertaking reviews in health care (PDF)

Further Readings

• Cochrane Handbook, part 2, chapter 4.6: Selecting studies This chapter details the requirements for authors performing screening for SRs in the health sciences.  
• Harrison, H., Griffin, S.J., Kuhn, I. et al. Software tools to support title and abstract screening for systematic reviews in healthcare: an evaluation . BMC Med Res Methodol 20, 7 (2020).  
• Micah D. J. Peters (2017) Managing and Coding References for Systematic Reviews and Scoping Reviews in EndNote , Medical Reference Services Quarterly, 36:1, 19-31, DOI:http://dx.doi.org/10.1080/02763869.2017.1259891
• Robin King, Barbara Hooper & Wendy Wood (2011) Using bibliographic software to appraise and code data in educational systematic review research , Medical Teacher, 33:9, 719-723, DOI: 10.3109/0142159X.2011.558138
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• Last Updated: Apr 3, 2024 11:48 AM
• URL: https://deakin.libguides.com/systematicreview

• Library Guides
• Literature Reviews
• Getting Started

Literature Reviews: Getting Started

What is a literature review.

A literature review is an overview of the available research for a specific scientific topic. Literature reviews summarize existing research to answer a review question, provide context for new research, or identify important gaps in the existing body of literature.

An incredible amount of academic literature is published each year, by estimates over two million articles .

Sorting through and reviewing that literature can be complicated, so this Research Guide provides a structured approach to make the process more manageable.

THIS GUIDE IS AN OVERVIEW OF THE LITERATURE REVIEW PROCESS:

• Getting Started (asking a research question | defining scope)
• Choosing a Type of Review
• Searching the Literature
• Organizing the Literature
• Writing the Literature Review (analyzing | synthesizing)

A  literature search  is a systematic search of the scholarly sources in a particular discipline. A  literature review   is the analysis, critical evaluation and synthesis of the results of that search. During this process you will move from a review  of  the literature to a review  for   your research.   Your synthesis of the literature is your unique contribution to research.

WHO IS THIS RESEARCH GUIDE FOR?

— those new to reviewing the literature

— those that need a refresher or a deeper understanding of writing literature reviews

You may need to do a literature review as a part of a course assignment, a capstone project, a master's thesis, a dissertation, or as part of a journal article. No matter the context, a literature review is an essential part of the research process. 

Literature Review Process

Purpose of a Literature Review

What is the purpose of a literature review.

A literature review is typically performed for a specific reason. Even when assigned as an assignment, the goal of the literature review will be one or more of the following:

• To communicate a project's novelty by identifying a research gap

• An overview of research issues , methodologies or results relevant to field
• To explore the  volume and types of available studies
• To establish familiarity with current research before carrying out a new project
• To resolve conflicts amongst contradictory previous studies

Reviewing the literature helps you understand a research topic and develop your own perspective.

A LITERATURE REVIEW IS NOT :

• An annotated bibliography – which is a list of annotated citations to books, articles and documents that includes a brief description and evaluation for each entry
• A literary review – which is a critical discussion of the merits and weaknesses of a literary work
• A book review – which is a critical discussion of the merits and weaknesses of a particular book

Attribution

Thanks to Librarian Jamie Niehof at the University of Michigan for providing permission to reuse and remix this Literature Reviews guide.

The Library's Subject Specialists are happy to help with your literature reviews!  Find your Subject Specialist here . 

If you have questions about this guide, contact Librarians Matt Upson ([email protected]), Dr. Frances Alvarado-Albertorio ([email protected]), or Clarke Iakovakis ([email protected])

• Last Updated: Apr 4, 2024 4:51 PM
• URL: https://info.library.okstate.edu/literaturereviews

Review Articles (Health Sciences)

• Finding Review Articles
• Goals of a Literature Review
• Select Citation Management Software
• Select databases to search
• Track your searches
• Conduct searches
• Select articles to include
• Extract information from articles
• Structure your review
• Find "fill-in" information
• Other sources and help
• Systematic Reviews
• Other types of reviews

The art of selecting articles from a list

Selecting articles to read from a results list is an art, not a science. Practicing makes it easier, which is why a literature review is a common assignment. Expect that you will be repeating the steps of searching and selecting articles several times; it is unlikely you will capture all needed materials in an initial search.

One possible method:

- Conduct a keyword search and locate a few somewhat-relevant looking articles

- Obtain the full text and read the articles.

- Consider: after reading these articles, which of my initial questions about this topic have been answered? What new or additional questions have I developed? Can I see any patterns or gaps starting to emerge in the literature? Use these new questions and patterns/gaps to help develop additional keywords to add to your search, to investigate another aspect of this topic.

- Repeat this process until you have answered your initial questions, answered new questions developed while reading, and can identify patterns/commonalities in the work, or can identify that there are few commonalities.

Do not expect to find any articles that cover your exact topic.  Expect to find articles that explain or investigate one or two aspects of your topic. Your job as the reviewer is to find articles that cover all aspects of the topic and combine their findings into a cohesive literature review.

Questions to be able to answer

A common question about literature reviews is knowing when to stop searching for additional materials. How will you know you have enough? Consider whether you could answer the relevant questions below; if you can, you may be ready to move on to writing.

1. Has your topic been studied a lot (over 200 articles a year on this topic) or a little? Why is there a large amount or little amount of research? Is it the same every year, or are there variances in publishing rates?

2. How has it been investigated before-- using prospective or retrospective research methods; which techniques or laboratory procedures? What was measured and using what scales or procedures? Can you characterize the results of the prior investigations? Are they uniform or do they vary widely?

3. When was this topic studied, and do my selected articles represent relevant time frames? Where has this topic been studied, and do my selected articles represent relevant locations?

4. If the topic I am investigating can affect a lot of people-- do I have representative information about a variety of people? From a variety of geographic locations, races/ethnicies, ages, locations of living (community-dwelling vs. hospital inpatients), gender, disease stage, etc? If I don't-- is this because I didn't look, because no one has studied this topic in this group, or because the topic doesn't affect this group?

5. To whom is this topic important- microbiologists, patients, occupational therapists, genetic counselors, etc.? Do I have perspectives written by and for the groups that are important to my topic?

6. How does my research project fit into this existing research? Do I offer a new perspective; develop a new technique; replicate the results of a study; answer questions that other researchers developed; fill in gaps in knowledge; etc.?

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• Last Updated: Nov 1, 2023 3:17 PM
• URL: https://libguides.usc.edu/healthsciences/reviewarticles

• Open access
• Published: 23 August 2022

Prognostic risk factors for moderate-to-severe exacerbations in patients with chronic obstructive pulmonary disease: a systematic literature review

• John R. Hurst 1 ,
• MeiLan K. Han 2 ,
• Barinder Singh 3 ,
• Sakshi Sharma 4 ,
• Gagandeep Kaur 3 ,
• Enrico de Nigris 5 ,
• Ulf Holmgren 6 &
• Mohd Kashif Siddiqui 3  

Respiratory Research volume  23 , Article number:  213 ( 2022 ) Cite this article

6315 Accesses

20 Citations

33 Altmetric

Metrics details

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide. COPD exacerbations are associated with a worsening of lung function, increased disease burden, and mortality, and, therefore, preventing their occurrence is an important goal of COPD management. This review was conducted to identify the evidence base regarding risk factors and predictors of moderate-to-severe exacerbations in patients with COPD.

A literature review was performed in Embase, MEDLINE, MEDLINE In-Process, and the Cochrane Central Register of Controlled Trials (CENTRAL). Searches were conducted from January 2015 to July 2019. Eligible publications were peer-reviewed journal articles, published in English, that reported risk factors or predictors for the occurrence of moderate-to-severe exacerbations in adults age ≥ 40 years with a diagnosis of COPD.

The literature review identified 5112 references, of which 113 publications (reporting results for 76 studies) met the eligibility criteria and were included in the review. Among the 76 studies included, 61 were observational and 15 were randomized controlled clinical trials. Exacerbation history was the strongest predictor of future exacerbations, with 34 studies reporting a significant association between history of exacerbations and risk of future moderate or severe exacerbations. Other significant risk factors identified in multiple studies included disease severity or bronchodilator reversibility (39 studies), comorbidities (34 studies), higher symptom burden (17 studies), and higher blood eosinophil count (16 studies).

Conclusions

This systematic literature review identified several demographic and clinical characteristics that predict the future risk of COPD exacerbations. Prior exacerbation history was confirmed as the most important predictor of future exacerbations. These prognostic factors may help clinicians identify patients at high risk of exacerbations, which are a major driver of the global burden of COPD, including morbidity and mortality.

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide [ 1 ]. Based upon disability-adjusted life-years, COPD ranked sixth out of 369 causes of global disease burden in 2019 [ 2 ]. COPD exacerbations are associated with a worsening of lung function, and increased disease burden and mortality (of those patients hospitalized for the first time with an exacerbation, > 20% die within 1 year of being discharged) [ 3 ]. Furthermore, patients with COPD consider exacerbations or hospitalization due to exacerbations to be the most important disease outcome, having a large impact on their lives [ 4 ]. Therefore, reducing the future risk of COPD exacerbations is a key goal of COPD management [ 5 ].

Being able to predict the level of risk for each patient allows clinicians to adapt treatment and patients to adjust their lifestyle (e.g., through a smoking cessation program) to prevent exacerbations [ 3 ]. As such, identifying high-risk patients using measurable risk factors and predictors that correlate with exacerbations is critical to reduce the burden of disease and prevent a cycle of decline encompassing irreversible lung damage, worsening quality of life (QoL), increasing disease burden, high healthcare costs, and early death.

Prior history of exacerbations is generally thought to be the best predictor of future exacerbations; however, there is a growing body of evidence suggesting other demographic and clinical characteristics, including symptom burden, airflow obstruction, comorbidities, and inflammatory biomarkers, also influence risk [ 6 , 7 , 8 , 9 ]. For example, in the prospective ECLIPSE observational study, the likelihood of patients experiencing an exacerbation within 1 year of follow-up increased significantly depending upon several factors, including prior exacerbation history, forced expiratory volume in 1 s (FEV 1 ), St. George’s Respiratory Questionnaire (SGRQ) score, gastroesophageal reflux, and white blood cell count [ 9 ].

Many studies have assessed predictors of COPD exacerbations across a variety of countries and patient populations. This systematic literature review (SLR) was conducted to identify and compile the evidence base regarding risk factors and predictors of moderate-to-severe exacerbations in patients with COPD.

• Systematic literature review

A comprehensive search strategy was designed to identify English-language studies published in peer-reviewed journals providing data on risk factors or predictors of moderate or severe exacerbations in adults aged ≥ 40 years with a diagnosis of COPD (sample size ≥ 100). The protocol is summarized in Table 1 and the search strategy is listed in Additional file 1 : Table S1. Key biomedical electronic literature databases were searched from January 2015 until July 2019. Other sources were identified via bibliographic searching of relevant systematic reviews.

Study selection process

Implementation and reporting followed the recommendations and standards of the Preferred Reporting Items for Systematic reviews and Meta-analyses (PRISMA) statement [ 10 ]. An independent reviewer conducted the first screening based on titles and abstracts, and a second reviewer performed a quality check of the excluded evidence. A single independent reviewer also conducted the second screening based on full-text articles, with a quality check of excluded evidence performed by a second reviewer. Likewise, data tables of the included studies were generated by one reviewer, and another reviewer performed a quality check of extracted data. Where more than one publication was identified describing a single study or trial, data were compiled into a single entry in the data-extraction table to avoid double counting of patients and studies. One publication was designated as the ‘primary publication’ for the purposes of the SLR, based on the following criteria: most recently published evidence and/or the article that presented the majority of data (e.g., journal articles were preferred over conference abstracts; articles that reported results for the full population were preferred over later articles providing results of subpopulations). Other publications reporting results from the same study were designated as ‘linked publications’; any additional data in the linked publications that were not included in the primary publication were captured in the SLR. Conference abstracts were excluded from the SLR unless they were a ‘linked publication.’

Included studies

A total of 5112 references (Fig.  1 ) were identified from the database searches. In total, 76 studies from 113 publications were included in the review. Primary publications and ‘linked publications’ for each study are detailed in Additional file 1 : Table S2, and study characteristics are shown in Additional file 1 : Table S3. The studies included clinical trials, registry studies, cross-sectional studies, cohort studies, database studies, and case–control studies. All 76 included studies were published in peer-reviewed journals. Regarding study design, 61 of the studies were observational (34 retrospective observational studies, 19 prospective observational studies, four cross-sectional studies, two studies with both retrospective and prospective cohort data, one case–control study, and one with cross-sectional and longitudinal data) and 15 were randomized controlled clinical trials.

PRISMA flow diagram of studies through the systematic review process. CA conference abstract, CENTRAL Cochrane Central Register of Controlled Trials, PRISMA  Preferred Reporting Items for Systematic Reviews and Meta-Analyses

Of the 76 studies, 16 were conducted in North America (13 studies in the USA, two in Canada, and one in Mexico); 26 were conducted in Europe (seven studies in Spain, four in the UK, three in Denmark, two studies each in Bulgaria, the Netherlands, and Switzerland, and one study each in Sweden, Serbia, Portugal, Greece, Germany, and France) and 17 were conducted in Asia (six studies in South Korea, four in China, three in Taiwan, two in Japan, and one study each in Singapore and Israel). One study each was conducted in Turkey and Australia. Fifteen studies were conducted across multiple countries.

The majority of the studies (n = 54) were conducted in a multicenter setting, while 22 studies were conducted in a single-center setting. The sample size among the included studies varied from 118 to 339,389 patients.

Patient characteristics

A total of 75 studies reported patient characteristics (Additional file 1 : Table S4). The mean age was reported in 65 studies and ranged from 58.0 to 75.2 years. The proportion of male patients ranged from 39.7 to 97.6%. The majority of included studies (85.3%) had a higher proportion of males than females.

Exacerbation history (as defined per each study) was reported in 18 of 76 included studies. The proportion of patients with no prior exacerbation was reported in ten studies (range, 0.1–79.5% of patients), one or fewer prior exacerbation in ten studies (range, 46–100%), one or more prior exacerbation in eight studies (range, 18.4–100%), and two or more prior exacerbations in 12 studies (range, 6.1–55.0%).

Prognostic factors of exacerbations

A summary of the risk factors and predictors reported across the included studies is provided in Tables 2 and 3 . The overall findings of the SLR are summarized in Figs. 2 and 3 .

Risk factors for moderate-to-severe exacerbations in patients with COPD. Factors with > 30 supporting studies shown as large circles; factors with ≤ 30 supporting studies shown as small circles and should be interpreted cautiously. BDR bronchodilator reversibility, BMI body mass index, COPD chronic obstructive pulmonary disease, EOS eosinophil, QoL quality of life

Summary of risk factors for exacerbation events. a Treatment impact studies removed. BDR bronchodilator reversibility, BMI body mass index, COPD chronic obstructive pulmonary disease, EOS eosinophil, QoL quality of life

Exacerbation history within the past 12 months was the strongest predictor of future exacerbations. Across the studies assessing this predictor, 34 out of 35 studies (97.1%) reported a significant association between history of exacerbations and risk of future moderate-to-severe exacerbations (Table 3 ). Specifically, two or more exacerbations in the previous year or at least one hospitalization for COPD in the previous year were identified as reliable predictors of future moderate or severe exacerbations. Even one moderate exacerbation increased the risk of a future exacerbation, with the risk increasing further with each subsequent exacerbation (Fig.  4 ). A severe exacerbation was also found to increase the risk of subsequent exacerbation and hospitalization (Fig.  5 ). Patients experiencing one or more severe exacerbations were more likely to experience further severe exacerbations than moderate exacerbations [ 11 , 12 ]. In contrast, patients with a history of one or more moderate exacerbations were more likely to experience further moderate exacerbations than severe exacerbations [ 11 , 12 ].

Exacerbation history as a risk factor for moderate-to-severe exacerbations. Yun 2018 included two studies; the study from which data were extracted (COPDGene or ECLIPSE) is listed in parentheses. CI confidence interval, ES effect size

Exacerbation history as a risk factor for severe exacerbations. Where data have been extracted from a linked publication rather than the primary publication, the linked publication is listed in parentheses. CI confidence interval, ES , effect size

Overall, 35 studies assessed the association of comorbidities with the risk of exacerbation. All studies except one (97.1%) reported a positive association between comorbidities and the occurrence of moderate-to-severe exacerbations (Table 3 ). In addition to the presence of any comorbidity, specific comorbidities that were found to significantly increase the risk of moderate-to-severe exacerbations included anxiety and depression, cardiovascular comorbidities, gastroesophageal reflux disease/dyspepsia, and respiratory comorbidities (Fig.  6 ). Comorbidities that were significant risk factors for severe exacerbations included cardiovascular, musculoskeletal, and respiratory comorbidities, diabetes, and malignancy (Fig.  7 ). Overall, the strongest association between comorbidities and COPD readmissions in the emergency department was with cardiovascular disease. The degree of risk for both moderate-to-severe and severe exacerbations also increased with the number of comorbidities. A Dutch cohort study found that 88% of patients with COPD had at least one comorbidity, with hypertension (35%) and coronary heart disease (19%) being the most prevalent. In this cohort, the comorbidities with the greatest risk of frequent exacerbations were pulmonary cancer (odds ratio [OR] 1.85) and heart failure (OR 1.72) [ 7 ].

Comorbidities as risk factors for moderate-to-severe exacerbations. Yun 2018 included two studies; the study from which data were extracted (COPDGene or ECLIPSE) is listed in parentheses. Where data have been extracted from a linked publication rather than the primary publication, the linked publication is listed in parentheses. CI confidence interval, ES effect size, GERD gastroesophageal disease

Comorbidities as risk factors for severe exacerbations. Where data have been extracted from a linked publication rather than the primary publication, the linked publication is listed in parentheses. CI confidence interval, CKD , chronic kidney disease, ES effect size

The majority of studies assessing disease severity or bronchodilator reversibility (39/41; 95.1%) indicated a significant positive relation between risk of future exacerbations and greater disease severity, as assessed by greater lung function impairment (in terms of lower FEV 1 , FEV 1 /forced vital capacity ratio, or forced expiratory flow [25–75]/forced vital capacity ratio) or more severe Global Initiative for Chronic Obstructive Lung Disease (GOLD) class A − D, and a positive relationship between risk of future exacerbations and lack of bronchodilator reversibility (Table 3 , Figs. 8 and 9 ).

Disease severity as a risk factor for moderate-to-severe exacerbations. Yun 2018 included two studies; the study from which data were extracted (COPDGene or ECLIPSE) is listed in parentheses. Where data have been extracted from a linked publication rather than the primary publication, the linked publication is listed in parentheses. CI confidence interval, ES effect size, FEV 1 f orced expiratory volume in 1 s, FVC , forced vital capacity, GOLD Global Initiative for Obstructive Lung Disease, HR hazard ratio, OR odds ratio

Disease severity and BDR as risk factors for severe exacerbations. ACCP American College of Chest Physicians, ACOS Asthma-COPD overlap syndrome, ATS  American Thoracic Society, BDR bronchodilator reversibility, CI confidence interval, ERS  European Respiratory Society, ES effect size, FEV 1 forced expiratory volume in 1 s, FVC  forced vital capacity, GINA Global Initiative for Asthma, GOLD Global Initiative for Obstructive Lung Disease

Of 21 studies assessing the relationship between blood eosinophil count and exacerbations (Table 3 ), 16 reported estimates for the risk of moderate or severe exacerbations by eosinophil count. A positive association was observed between higher eosinophil count and a higher risk of moderate or severe exacerbations, particularly in patients not treated with an inhaled corticosteroid (ICS); however, five studies reported a significant positive association irrespective of intervention effects. The risk of moderate-to-severe exacerbations was observed to be positively associated with various definitions of higher eosinophil levels (absolute counts: ≥ 200, ≥ 300, ≥ 340, ≥ 400, and ≥ 500 cells/mm 3 ; % of blood eosinophil count: ≥ 2%, ≥ 3%, ≥ 4%, and ≥ 5%). Of note, one study found reduced efficacy of ICS in lowering moderate-to-severe exacerbation rates for current smokers versus former smokers at all eosinophil levels [ 13 ].

Of 12 studies assessing QoL scales, 11 (91.7%) studies reported a significant association between the worsening of QoL scores and the risk of future exacerbations (Table 3 ). Baseline SGRQ [ 14 , 15 ], Center for Epidemiologic Studies Depression Scale (for which increased scores may indicate impaired QoL) [ 16 ], and Clinical COPD Questionnaire [ 17 , 18 ] scores were found to be associated with future risk of moderate and/or severe COPD exacerbations. For symptom scores, six out of eight studies assessing the association between moderate-to-severe or severe exacerbations with COPD Assessment Test (CAT) scores reported a significant and positive relationship. Furthermore, the risk of moderate-to-severe exacerbations was found to be significantly higher in patients with higher CAT scores (≥ 10) [ 15 , 19 , 20 , 21 ], with one study demonstrating that a CAT score of 15 increased predictive ability for exacerbations compared with a score of 10 or more [ 18 ]. Among 15 studies that assessed the association of modified Medical Research Council (mMRC) scores with the risk of moderate-to-severe or severe exacerbation, 11 found that the risk of moderate-to-severe or severe exacerbations was significantly associated with higher mMRC scores (≥ 2) versus lower scores. Furthermore, morning and night symptoms (measured by Clinical COPD Questionnaire) were associated with poor health status and predicted future exacerbations [ 17 ].

Of 36 studies reporting the relationship between smoking status and moderate-to-severe or severe exacerbations, 22 studies (61.1%) reported a significant positive association (Table 3 ). Passive smoking was also significantly associated with an increased risk of severe exacerbations (OR 1.49) [ 20 ]. Of note, three studies reported a significantly lower rate of moderate-to-severe exacerbations in current smokers compared with former smokers [ 22 , 23 , 24 ].

A total of 14 studies assessed the association of body mass index (BMI) with the occurrence of frequent moderate-to-severe exacerbations in patients with COPD. Six out of 14 studies (42.9%) reported a significant negative association between exacerbations and BMI (Table 3 ). The risk of moderate and/or severe COPD exacerbations was highest among underweight patients compared with normal and overweight patients [ 23 , 25 , 26 , 27 , 28 ].

In the 29 studies reporting an association between age and moderate or severe exacerbations, more than half found an association of older age with an increased risk of moderate-to-severe exacerbations (58.6%; Table 3 ). Four of these studies noted a significant increase in the risk of moderate-to-severe or severe exacerbations for every 10-year increase in age [ 25 , 26 , 29 , 30 ]. However, 12 studies reported no significant association between age and moderate-to-severe or severe exacerbation risk.

Sixteen out of 33 studies investigating the impact of sex on exacerbation risk found a significant association (48.5%; Table 3 ). Among these, ten studies reported that female sex was associated with an increased risk of moderate-to-severe exacerbations, while six studies showed a higher exacerbation risk in males compared with females. There was some variation in findings by geographic location and exacerbation severity (Additional file 2 : Figs. S1 and S2). Notably, when assessing the risk of severe exacerbations, more studies found an association with male sex compared with female sex (6/13 studies vs 1/13 studies, respectively).

Both studies evaluating associations between exacerbations and environmental factors reported that colder temperature and exposure to major air pollution (NO 2 , O 3 , CO, and/or particulate matter ≤ 10 μm in diameter) increased hospital admissions due to severe exacerbations and moderate-to-severe exacerbation rates [ 31 , 32 ].

Four studies assessed the association of 6-min walk distance with the occurrence of frequent moderate-to-severe exacerbations (Table 3 ). One study (25.0%) found that shorter 6-min walk distance (representing low physical activity) was significantly associated with a shortened time to severe exacerbation, but the effect size was small (hazard ratio 0.99) [ 33 ].

Five out of six studies assessing the relationship between race or ethnicity and exacerbation risk reported significant associations (Table 3 ). Additionally, one study reported an association between geographic location in the US and exacerbations, with living in the Northeast region being the strongest predictor of severe COPD exacerbations versus living in the Midwest and South regions [ 34 ].

Overall, seven studies assessed the association of biomarkers with risk of future exacerbations (Table 3 ), with the majority identifying significant associations between inflammatory biomarkers and increased exacerbation risk, including higher C-reactive protein levels [ 8 , 35 ], fibrinogen levels [ 8 , 30 ], and white blood cell count [ 8 , 15 , 16 ].

This SLR has identified several demographic and clinical characteristics that predict the future risk of COPD exacerbations. Key factors associated with an increased risk of future moderate-to-severe exacerbations included a history of prior exacerbations, worse disease severity and bronchodilator reversibility, the presence of comorbidities, a higher eosinophil count, and older age (Fig.  2 ). These prognostic factors may help clinicians identify patients at high risk of exacerbations, which are a major driver of the burden of COPD, including morbidity and mortality [ 36 ].

Findings from this review summarize the existing evidence, validating the previously published literature [ 6 , 9 , 23 ] and suggesting that the best predictor of future exacerbations is a history of exacerbations in the prior year [ 8 , 11 , 12 , 13 , 14 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 26 , 29 , 34 , 35 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ]. In addition, the effect size generally increased with the number of prior exacerbations, with a stronger effect observed with prior severe versus moderate exacerbations. This effect was observed across regions, including in Europe and North America, and in several global studies. This relationship represents a vicious circle, whereby one exacerbation predisposes a patient to experience future exacerbations and leading to an ever-increasing disease burden, and emphasizes the importance of preventing the first exacerbation event through early, proactive exacerbation prevention. The finding that prior exacerbations tended to be associated with future exacerbations of the same severity suggests that the severity of the underlying disease may influence exacerbation severity. However, the validity of the traditional classification of exacerbation severity has recently been challenged [ 61 ], and further work is required to understand relationships with objective assessments of exacerbation severity.

In addition to exacerbation history, disease severity and bronchodilator reversibility were also strong predictors for future exacerbations [ 8 , 14 , 16 , 18 , 19 , 20 , 22 , 23 , 24 , 26 , 28 , 29 , 33 , 37 , 40 , 43 , 44 , 45 , 46 , 48 , 50 , 51 , 52 , 56 , 59 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 ]. The association with disease severity was noted in studies that used GOLD disease stages 1–4 and those that used FEV 1 percent predicted and other lung function assessments as continuous variables. Again, this risk factor is self-perpetuating, as evidence shows that even a single moderate or severe exacerbation may almost double the rate of lung function decline [ 79 ]. Accordingly, disease severity and exacerbation history may be correlated. Margüello et al. concluded that the severity of COPD could be associated with a higher risk of exacerbations, but this effect was partly determined by the exacerbations suffered in the previous year [ 23 ]. It should be noted that FEV 1 is not recommended by GOLD for use as a predictor of exacerbation risk or mortality alone due to insufficient precision when used at the individual patient level [ 5 ].

Another factor that should be considered when assessing individual exacerbation risk is the presence of comorbidities [ 7 , 14 , 16 , 18 , 19 , 20 , 21 , 22 , 24 , 25 , 26 , 27 , 28 , 30 , 33 , 34 , 35 , 40 , 41 , 44 , 45 , 46 , 47 , 48 , 51 , 52 , 53 , 54 , 56 , 58 , 59 , 63 , 64 , 73 , 74 , 76 , 77 , 80 , 81 , 82 , 83 , 84 , 85 ]. Comorbidities are common in COPD, in part due to common risk factors (e.g., age, smoking, lifestyle factors) that also increase the risk of other chronic diseases [ 7 ]. Significant associations were observed between exacerbation risk and comorbidities, such as anxiety and depression, cardiovascular disease, diabetes, and respiratory comorbidities. As with prior exacerbations, the strength of the association increased with the number of comorbidities. Some comorbidities that were found to be associated with COPD exacerbations share a common biological mechanism of systemic inflammation, such as cardiovascular disease, diabetes, and depression [ 86 ]. Furthermore, other respiratory comorbidities, including asthma and bronchiectasis, involve inflammation of the airways [ 87 ]. In these patients, optimal management of comorbidities may reduce the risk of future COPD exacerbations (and improve QoL), although further research is needed to confirm the efficacy of this approach to exacerbation prevention. As cardiovascular conditions, including hypertension and coronary heart disease, are the most common comorbidities in people with COPD [ 7 ], reducing cardiovascular risk may be a key goal in reducing the occurrence of exacerbations. For other comorbidities, the mechanism for the association with exacerbation risk may be related to non-biological factors. For example, in depression, it has been suggested that the mechanism may relate to greater sensitivity to symptom changes or more frequent physician visits [ 88 ].

There is now a growing body of evidence reporting the relationship between blood eosinophil count and exacerbation risk [ 8 , 13 , 14 , 20 , 37 , 48 , 52 , 56 , 59 , 60 , 62 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 ]. Data from many large clinical trials (SUNSET [ 89 ], FLAME [ 96 ], WISDOM [ 98 ], IMPACT [ 13 ], TRISTAN [ 99 ], INSPIRE [ 99 ], KRONOS [ 91 ], TRIBUTE [ 48 ], TRILOGY [ 52 ], TRINITY [ 56 ]) have also shown relationships between treatment, eosinophil count, and exacerbation rates. Evidence shows that eosinophil count, along with other effect modifiers (e.g., exacerbation history), can be used to predict reductions in exacerbations with ICS treatment. Identifying patients most likely to respond to ICS should contribute to personalized medicine approaches to treat COPD. One challenge in drawing a strong conclusion from eosinophil counts is the choice of a cut-off value, with a variety of absolute and percentage values observed to be positively associated with the risk of moderate-to-severe exacerbations. The use of absolute counts may be more practical, as these are not affected by variations in other immune cell numbers; however, there is a lack of consensus on this point [ 100 ].

Across the studies examined, associations between sex and the risk of moderate and/or severe exacerbations were variable [ 14 , 16 , 18 , 20 , 21 , 22 , 23 , 24 , 26 , 27 , 28 , 29 , 37 , 40 , 42 , 44 , 45 , 46 , 47 , 48 , 51 , 52 , 56 , 58 , 59 , 63 , 73 , 74 , 77 , 80 , 83 , 84 , 85 ]. A greater number of studies showed an increased risk of exacerbations in females compared with males. In contrast, some studies failed to detect a relationship, suggesting that country-specific or cultural factors may play a role. A majority of the included studies evaluated more male patients than female patients; to further elucidate the relationship between sex and exacerbations, more studies in female patients are warranted. Over half of the studies that assessed the relationship between age and exacerbation risk found an association between increasing age and increasing risk of moderate-to-severe COPD exacerbations [ 14 , 16 , 18 , 20 , 21 , 22 , 23 , 24 , 26 , 27 , 28 , 29 , 33 , 40 , 42 , 44 , 45 , 47 , 51 , 52 , 54 , 56 , 63 , 73 , 74 , 77 , 80 , 83 , 85 ].

Our findings also suggested that patients with low BMI have greater risk of moderate and/or severe exacerbations. The mechanism underlying this increased risk in underweight patients is poorly understood; however, loss of lean body mass in patients with COPD may be related to ongoing systemic inflammation that impacts skeletal muscle mass [ 101 , 102 , 103 ].

A limitation of this SLR, that may have resulted in some studies with valid results being missed, was the exclusion of non-English-language studies and the limitation by date; however, the search strategy was otherwise broad, resulting in the review of a large number of studies. The majority of studies captured in this SLR were from Europe, North America, and Asia. The findings may therefore be less generalizable to patients in other regions, such as Africa or South America. Given that one study reported an association between geographic location within different regions of the US and exacerbations [ 34 ], it is plausible that risk of exacerbations may be impacted by global location. As no formal meta-analysis was planned, the assessments are based on a qualitative synthesis of studies. A majority of the included studies looked at exposures of certain factors (e.g., history of exacerbations) at baseline; however, some of these factors change over time, calling into question whether a more sophisticated statistical analysis should have been conducted in some cases to consider time-varying covariates. Our results can only inform on associations, not causation, and there are likely bidirectional relationships between many factors and exacerbation risk (e.g., health status). Finally, while our review of the literature captured a large number of prognostic factors, other variables such as genetic factors, lung microbiome composition, and changes in therapy over time have not been widely studied to date, but might also influence exacerbation frequency [ 104 ]. Further research is needed to assess the contribution of these factors to exacerbation risk.

This SLR captured publications up to July 2019. However, further studies have since been published that further support the prognostic factors identified here. For example, recent studies have reported an increased risk of exacerbations in patients with a history of exacerbations [ 105 ], comorbidities [ 106 ], poorer lung function (GOLD stage) [ 105 ], higher symptomatic burden [ 107 ], female sex [ 105 ], and lower BMI [ 106 , 108 ].

In summary, the literature assessing risk factors for moderate-to-severe COPD exacerbations shows that there are associations between several demographic and disease characteristics with COPD exacerbations, potentially allowing clinicians to identify patients most at risk of future exacerbations. Exacerbation history, comorbidities, and disease severity or bronchodilator reversibility were the factors most strongly associated with exacerbation risk, and should be considered in future research efforts to develop prognostic tools to estimate the likelihood of exacerbation occurrence. Importantly, many prognostic factors for exacerbations, such as symptom burden, QoL, and comorbidities, are modifiable with optimal pharmacologic and non-pharmacologic treatments or lifestyle modifications. Overall, the evidence suggests that, taken together, predicting and reducing exacerbation risk is an achievable goal in COPD.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Abbreviations

Body mass index

COPD Assessment Test

Chronic obstructive pulmonary disease

Forced expiratory volume in 1 s

Global Initiative for Chronic Obstructive Lung Disease

Inhaled corticosteroid

Modified Medical Research Council

Quality of life

St. George’s Respiratory Questionnaire

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Acknowledgements

Medical writing support, under the direction of the authors, was provided by Julia King, PhD, and Sarah Piggott, MChem, CMC Connect, McCann Health Medical Communications, funded by AstraZeneca in accordance with Good Publication Practice (GPP3) guidelines [ 109 ].

This study was supported by AstraZeneca.

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The authors have made the following declaration about their contributions. JRH and MKH made substantial contributions to the interpretation of data; BS, SS, GK, and MKS made substantial contributions to the acquisition, analysis, and interpretation of data; EdN and UH made substantial contributions to the conception and design of the work and the interpretation of data. All authors contributed to drafting or critically revising the article, have approved the submitted version, and agree to be personally accountable for their own contributions and to ensure that questions related to the accuracy or integrity of any part of the work, even ones in which the author was not personally involved, are appropriately investigated, resolved, and the resolution documented in the literature. All authors read and approved the final manuscript.

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JRH reports consulting fees from AstraZeneca; speaker fees from AstraZeneca, Chiesi, Pfizer, and Takeda; and travel support from GlaxoSmithKline and AstraZeneca. MKH reports assistance with conduction of this research and publication from AstraZeneca; personal fees from Aerogen, Altesa Biopharma, AstraZeneca, Boehringer Ingelheim, Chiesi, Cipla, DevPro, GlaxoSmithKline, Integrity, Medscape, Merck, Mylan, NACE, Novartis, Polarean, Pulmonx, Regeneron, Sanofi, Teva, Verona, United Therapeutics, and UpToDate; either in kind research support or funds paid to the institution from the American Lung Association, AstraZeneca, Biodesix, Boehringer Ingelheim, the COPD Foundation, Gala Therapeutics, the NIH, Novartis, Nuvaira, Sanofi, and Sunovion; participation in Data Safety Monitoring Boards for Novartis and Medtronic with funds paid to the institution; and stock options from Altesa Biopharma and Meissa Vaccines. BS, GK, and MKS are former employees of Parexel International. SS is an employee of Parexel International, which was funded by AstraZeneca to conduct this analysis. EdN is a former employee of AstraZeneca and previously held stock and/or stock options in the company. UH is an employee of AstraZeneca and holds stock and/or stock options in the company.

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Supplementary Information

Additional file1: table s1..

Search strategies. Table S2. List of included studies with linked publications. Table S3. Study characteristics across the 76 included studies. Table S4. Clinical characteristics of the patients assessed across the included studies.

Additional file 2: Fig. S1.

Sex (male vs female) as a risk factor for moderate-to-severe exacerbations. Fig. S2. Sex (male vs female) as a risk factor for severe exacerbations.

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Hurst, J.R., Han, M.K., Singh, B. et al. Prognostic risk factors for moderate-to-severe exacerbations in patients with chronic obstructive pulmonary disease: a systematic literature review. Respir Res 23 , 213 (2022). https://doi.org/10.1186/s12931-022-02123-5

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Examining the role of community resilience and social capital on mental health in public health emergency and disaster response: a scoping review

• C. E. Hall 1 , 2 ,
• H. Wehling 1 ,
• J. Stansfield 3 ,
• J. South 3 ,
• S. K. Brooks 2 ,
• N. Greenberg 2 , 4 ,
• R. Amlôt 1 &
• D. Weston 1  

BMC Public Health volume  23 , Article number:  2482 ( 2023 ) Cite this article

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The ability of the public to remain psychologically resilient in the face of public health emergencies and disasters (such as the COVID-19 pandemic) is a key factor in the effectiveness of a national response to such events. Community resilience and social capital are often perceived as beneficial and ensuring that a community is socially and psychologically resilient may aid emergency response and recovery. This review presents a synthesis of literature which answers the following research questions: How are community resilience and social capital quantified in research?; What is the impact of community resilience on mental wellbeing?; What is the impact of infectious disease outbreaks, disasters and emergencies on community resilience and social capital?; and, What types of interventions enhance community resilience and social capital?

A scoping review procedure was followed. Searches were run across Medline, PsycInfo, and EMBASE, with search terms covering both community resilience and social capital, public health emergencies, and mental health. 26 papers met the inclusion criteria.

The majority of retained papers originated in the USA, used a survey methodology to collect data, and involved a natural disaster. There was no common method for measuring community resilience or social capital. The association between community resilience and social capital with mental health was regarded as positive in most cases. However, we found that community resilience, and social capital, were initially negatively impacted by public health emergencies and enhanced by social group activities.

Several key recommendations are proposed based on the outcomes from the review, which include: the need for a standardised and validated approach to measuring both community resilience and social capital; that there should be enhanced effort to improve preparedness to public health emergencies in communities by gauging current levels of community resilience and social capital; that community resilience and social capital should be bolstered if areas are at risk of disasters or public health emergencies; the need to ensure that suitable short-term support is provided to communities with high resilience in the immediate aftermath of a public health emergency or disaster; the importance of conducting robust evaluation of community resilience initiatives deployed during the COVID-19 pandemic.

Peer Review reports

For the general population, public health emergencies and disasters (e.g., natural disasters; infectious disease outbreaks; Chemical, Biological, Radiological or Nuclear incidents) can give rise to a plethora of negative outcomes relating to both health (e.g. increased mental health problems [ 1 , 2 , 3 , 4 ]) and the economy (e.g., increased unemployment and decreased levels of tourism [ 4 , 5 , 6 ]). COVID-19 is a current, and ongoing, example of a public health emergency which has affected over 421 million individuals worldwide [ 7 ]. The long term implications of COVID-19 are not yet known, but there are likely to be repercussions for physical health, mental health, and other non-health related outcomes for a substantial time to come [ 8 , 9 ]. As a result, it is critical to establish methods which may inform approaches to alleviate the longer-term negative consequences that are likely to emerge in the aftermath of both COVID-19 and any future public health emergency.

The definition of resilience often differs within the literature, but ultimately resilience is considered a dynamic process of adaptation. It is related to processes and capabilities at the individual, community and system level that result in good health and social outcomes, in spite of negative events, serious threats and hazards [ 10 ]. Furthermore, Ziglio [ 10 ] refers to four key types of resilience capacity: adaptive, the ability to withstand and adjust to unfavourable conditions and shocks; absorptive, the ability to withstand but also to recover and manage using available assets and skills; anticipatory, the ability to predict and minimize vulnerability; and transformative, transformative change so that systems better cope with new conditions.

There is no one settled definition of community resilience (CR). However, it generally relates to the ability of a community to withstand, adapt and permit growth in adverse circumstances due to social structures, networks and interdependencies within the community [ 11 ]. Social capital (SC) is considered a major determinant of CR [ 12 , 13 ], and reflects strength of a social network, community reciprocity, and trust in people and institutions [ 14 ]. These aspects of community are usually conceptualised primarily as protective factors that enable communities to cope and adapt collectively to threats. SC is often broken down into further categories [ 15 ], for example: cognitive SC (i.e. perceptions of community relations, such as trust, mutual help and attachment) and structural SC (i.e. what actually happens within the community, such as participation, socialising) [ 16 ]; or, bonding SC (i.e. connections among individuals who are emotionally close, and result in bonds to a particular group [ 17 ]) and bridging SC (i.e. acquaintances or individuals loosely connected that span different social groups [ 18 ]). Generally, CR is perceived to be primarily beneficial for multiple reasons (e.g. increased social support [ 18 , 19 ], protection of mental health [ 20 , 21 ]), and strengthening community resilience is a stated health goal of the World Health Organisation [ 22 ] when aiming to alleviate health inequalities and protect wellbeing. This is also reflected by organisations such as Public Health England (now split into the UK Health Security Agency and the Office for Health Improvement and Disparities) [ 23 ] and more recently, CR has been targeted through the endorsement of Community Champions (who are volunteers trained to support and to help improve health and wellbeing. Community Champions also reflect their local communities in terms of population demographics for example age, ethnicity and gender) as part of the COVID-19 response in the UK (e.g. [ 24 , 25 ]).

Despite the vested interest in bolstering communities, the research base establishing: how to understand and measure CR and SC; the effect of CR and SC, both during and following a public health emergency (such as the COVID-19 pandemic); and which types of CR or SC are the most effective to engage, is relatively small. Given the importance of ensuring resilience against, and swift recovery from, public health emergencies, it is critically important to establish and understand the evidence base for these approaches. As a result, the current review sought to answer the following research questions: (1) How are CR and SC quantified in research?; (2) What is the impact of community resilience on mental wellbeing?; (3) What is the impact of infectious disease outbreaks, disasters and emergencies on community resilience and social capital?; and, (4) What types of interventions enhance community resilience and social capital?

By collating research in order to answer these research questions, the authors have been able to propose several key recommendations that could be used to both enhance and evaluate CR and SC effectively to facilitate the long-term recovery from COVID-19, and also to inform the use of CR and SC in any future public health disasters and emergencies.

A scoping review methodology was followed due to the ease of summarising literature on a given topic for policy makers and practitioners [ 26 ], and is detailed in the following sections.

Identification of relevant studies

An initial search strategy was developed by authors CH and DW and included terms which related to: CR and SC, given the absence of a consistent definition of CR, and the link between CR and SC, the review focuses on both CR and SC to identify as much relevant literature as possible (adapted for purpose from Annex 1: [ 27 ], as well as through consultation with review commissioners); public health emergencies and disasters [ 28 , 29 , 30 , 31 ], and psychological wellbeing and recovery (derived a priori from literature). To ensure a focus on both public health and psychological research, the final search was carried across Medline, PsycInfo, and EMBASE using OVID. The final search took place on the 18th of May 2020, the search strategy used for all three databases can be found in Supplementary file 1 .

Selection criteria

The inclusion and exclusion criteria were developed alongside the search strategy. Initially the criteria were relatively inclusive and were subject to iterative development to reflect the authors’ familiarisation with the literature. For example, the decision was taken to exclude research which focused exclusively on social support and did not mention communities as an initial title/abstract search suggested that the majority of this literature did not meet the requirements of our research question.

The full and final inclusion and exclusion criteria used can be found in Supplementary file 2 . In summary, authors decided to focus on the general population (i.e., non-specialist, e.g. non-healthcare worker or government official) to allow the review to remain community focused. The research must also have assessed the impact of CR and/or SC on mental health and wellbeing, resilience, and recovery during and following public health emergencies and infectious disease outbreaks which affect communities (to ensure the research is relevant to the review aims), have conducted primary research, and have a full text available or provided by the first author when contacted.

Charting the data

All papers were first title and abstract screened by CH or DW. Papers then were full text reviewed by CH to ensure each paper met the required eligibility criteria, if unsure about a paper it was also full text reviewed by DW. All papers that were retained post full-text review were subjected to a standardised data extraction procedure. A table was made for the purpose of extracting the following data: title, authors, origin, year of publication, study design, aim, disaster type, sample size and characteristics, variables examined, results, restrictions/limitations, and recommendations. Supplementary file 3 details the charting the data process.

Analytical method

Data was synthesised using a Framework approach [ 32 ], a common method for analysing qualitative research. This method was chosen as it was originally used for large-scale social policy research [ 33 ] as it seeks to identify: what works, for whom, in what conditions, and why [ 34 ]. This approach is also useful for identifying commonalities and differences in qualitative data and potential relationships between different parts of the data [ 33 ]. An a priori framework was established by CH and DW. Extracted data was synthesised in relation to each research question, and the process was iterative to ensure maximum saturation using the available data.

Study selection

The final search strategy yielded 3584 records. Following the removal of duplicates, 2191 records remained and were included in title and abstract screening. A PRISMA flow diagram is presented in Fig.  1 .

PRISMA flow diagram

At the title and abstract screening stage, the process became more iterative as the inclusion criteria were developed and refined. For the first iteration of screening, CH or DW sorted all records into ‘include,’ ‘exclude,’ and ‘unsure’. All ‘unsure’ papers were re-assessed by CH, and a random selection of ~ 20% of these were also assessed by DW. Where there was disagreement between authors the records were retained, and full text screened. The remaining papers were reviewed by CH, and all records were categorised into ‘include’ and ‘exclude’. Following full-text screening, 26 papers were retained for use in the review.

Study characteristics

This section of the review addresses study characteristics of those which met the inclusion criteria, which comprises: date of publication, country of origin, study design, study location, disaster, and variables examined.

Date of publication

Publication dates across the 26 papers spanned from 2008 to 2020 (see Fig.  2 ). The number of papers published was relatively low and consistent across this timescale (i.e. 1–2 per year, except 2010 and 2013 when none were published) up until 2017 where the number of papers peaked at 5. From 2017 to 2020 there were 15 papers published in total. The amount of papers published in recent years suggests a shift in research and interest towards CR and SC in a disaster/ public health emergency context.

Graph to show retained papers date of publication

Country of origin

The locations of the first authors’ institutes at the time of publication were extracted to provide a geographical spread of the retained papers. The majority originated from the USA [ 35 , 36 , 37 , 38 , 39 , 40 , 41 ], followed by China [ 42 , 43 , 44 , 45 , 46 ], Japan [ 47 , 48 , 49 , 50 ], Australia [ 51 , 52 , 53 ], The Netherlands [ 54 , 55 ], New Zealand [ 56 ], Peru [ 57 ], Iran [ 58 ], Austria [ 59 ], and Croatia [ 60 ].

There were multiple methodological approaches carried out across retained papers. The most common formats included surveys or questionnaires [ 36 , 37 , 38 , 42 , 46 , 47 , 48 , 49 , 50 , 53 , 54 , 55 , 57 , 59 ], followed by interviews [ 39 , 40 , 43 , 51 , 52 , 60 ]. Four papers used both surveys and interviews [ 35 , 41 , 45 , 58 ], and two papers conducted data analysis (one using open access data from a Social Survey [ 44 ] and one using a Primary Health Organisations Register [ 56 ]).

Study location

The majority of the studies were carried out in Japan [ 36 , 42 , 44 , 47 , 48 , 49 , 50 ], followed by the USA [ 35 , 37 , 38 , 39 , 40 , 41 ], China [ 43 , 45 , 46 , 53 ], Australia [ 51 , 52 ], and the UK [ 54 , 55 ]. The remaining studies were carried out in Croatia [ 60 ], Peru [ 57 ], Austria [ 59 ], New Zealand [ 56 ] and Iran [ 58 ].

Multiple different types of disaster were researched across the retained papers. Earthquakes were the most common type of disaster examined [ 45 , 47 , 49 , 50 , 53 , 56 , 57 , 58 ], followed by research which assessed the impact of two disastrous events which had happened in the same area (e.g. Hurricane Katrina and the Deepwater Horizon oil spill in Mississippi, and the Great East Japan earthquake and Tsunami; [ 36 , 37 , 38 , 42 , 44 , 48 ]). Other disaster types included: flooding [ 51 , 54 , 55 , 59 , 60 ], hurricanes [ 35 , 39 , 41 ], infectious disease outbreaks [ 43 , 46 ], oil spillage [ 40 ], and drought [ 52 ].

Variables of interest examined

Across the 26 retained papers: eight referred to examining the impact of SC [ 35 , 37 , 39 , 41 , 46 , 49 , 55 , 60 ]; eight examined the impact of cognitive and structural SC as separate entities [ 40 , 42 , 45 , 48 , 50 , 54 , 57 , 59 ]; one examined bridging and bonding SC as separate entities [ 58 ]; two examined the impact of CR [ 38 , 56 ]; and two employed a qualitative methodology but drew findings in relation to bonding and bridging SC, and SC generally [ 51 , 52 ]. Additionally, five papers examined the impact of the following variables: ‘community social cohesion’ [ 36 ], ‘neighbourhood connectedness’ [ 44 ], ‘social support at the community level’ [ 47 ], ‘community connectedness’ [ 43 ] and ‘sense of community’ [ 53 ]. Table  1 provides additional details on this.

How is CR and SC measured or quantified in research?

The measures used to examine CR and SC are presented Table  1 . It is apparent that there is no uniformity in how SC or CR is measured across the research. Multiple measures are used throughout the retained studies, and nearly all are unique. Additionally, SC was examined at multiple different levels (e.g. cognitive and structural, bonding and bridging), and in multiple different forms (e.g. community connectedness, community cohesion).

What is the association between CR and SC on mental wellbeing?

To best compare research, the following section reports on CR, and facets of SC separately. Please see Supplementary file 4  for additional information on retained papers methods of measuring mental wellbeing.

• Community resilience

CR relates to the ability of a community to withstand, adapt and permit growth in adverse circumstances due to social structures, networks and interdependencies within the community [ 11 ].

The impact of CR on mental wellbeing was consistently positive. For example, research indicated that there was a positive association between CR and number of common mental health (i.e. anxiety and mood) treatments post-disaster [ 56 ]. Similarly, other research suggests that CR is positively related to psychological resilience, which is inversely related to depressive symptoms) [ 37 ]. The same research also concluded that CR is protective of psychological resilience and is therefore protective of depressive symptoms [ 37 ].

• Social capital

SC reflects the strength of a social network, community reciprocity, and trust in people and institutions [ 14 ]. These aspects of community are usually conceptualised primarily as protective factors that enable communities to cope and adapt collectively to threats.

There were inconsistencies across research which examined the impact of abstract SC (i.e. not refined into bonding/bridging or structural/cognitive) on mental wellbeing. However, for the majority of cases, research deems SC to be beneficial. For example, research has concluded that, SC is protective against post-traumatic stress disorder [ 55 ], anxiety [ 46 ], psychological distress [ 50 ], and stress [ 46 ]. Additionally, SC has been found to facilitate post-traumatic growth [ 38 ], and also to be useful to be drawn upon in times of stress [ 52 ], both of which could be protective of mental health. Similarly, research has also found that emotional recovery following a disaster is more difficult for those who report to have low levels of SC [ 51 ].

Conversely, however, research has also concluded that when other situational factors (e.g. personal resources) were controlled for, a positive relationship between community resources and life satisfaction was no longer significant [ 60 ]. Furthermore, some research has concluded that a high level of SC can result in a community facing greater stress immediately post disaster. Indeed, one retained paper found that high levels of SC correlate with higher levels of post-traumatic stress immediately following a disaster [ 39 ]. However, in the later stages following a disaster, this relationship can reverse, with SC subsequently providing an aid to recovery [ 41 ]. By way of explanation, some researchers have suggested that communities with stronger SC carry the greatest load in terms of helping others (i.e. family, friends and neighbours) as well as themselves immediately following the disaster, but then as time passes the communities recover at a faster rate as they are able to rely on their social networks for support [ 41 ].

Cognitive and structural social capital

Cognitive SC refers to perceptions of community relations, such as trust, mutual help and attachment, and structural SC refers to what actually happens within the community, such as participation, socialising [ 16 ].

Cognitive SC has been found to be protective [ 49 ] against PTSD [ 54 , 57 ], depression [ 40 , 54 ]) mild mood disorder; [ 48 ]), anxiety [ 48 , 54 ] and increase self-efficacy [ 59 ].

For structural SC, research is again inconsistent. On the one hand, structural SC has been found to: increase perceived self-efficacy, be protective of depression [ 40 ], buffer the impact of housing damage on cognitive decline [ 42 ] and provide support during disasters and over the recovery period [ 59 ]. However, on the other hand, it has been found to have no association with PTSD [ 54 , 57 ] or depression, and is also associated with a higher prevalence of anxiety [ 54 ]. Similarly, it is also suggested by additional research that structural SC can harm women’s mental health, either due to the pressure of expectations to help and support others or feelings of isolation [ 49 ].

Bonding and bridging social capital

Bonding SC refers to connections among individuals who are emotionally close, and result in bonds to a particular group [ 17 ], and bridging SC refers to acquaintances or individuals loosely connected that span different social groups [ 18 ].

One research study concluded that both bonding and bridging SC were protective against post-traumatic stress disorder symptoms [ 58 ]. Bridging capital was deemed to be around twice as effective in buffering against post-traumatic stress disorder than bonding SC [ 58 ].

Other community variables

Community social cohesion was significantly associated with a lower risk of post-traumatic stress disorder symptom development [ 35 ], and this was apparent even whilst controlling for depressive symptoms at baseline and disaster impact variables (e.g. loss of family member or housing damage) [ 36 ]. Similarly, sense of community, community connectedness, social support at the community level and neighbourhood connectedness all provided protective benefits for a range of mental health, wellbeing and recovery variables, including: depression [ 53 ], subjective wellbeing (in older adults only) [ 43 ], psychological distress [ 47 ], happiness [ 44 ] and life satisfaction [ 53 ].

Research has also concluded that community level social support is protective against mild mood and anxiety disorder, but only for individuals who have had no previous disaster experience [ 48 ]. Additionally, a study which separated SC into social cohesion and social participation concluded that at a community level, social cohesion is protective against depression [ 49 ] whereas social participation at community level is associated with an increased risk of depression amongst women [ 49 ].

What is the impact of Infectious disease outbreaks / disasters and emergencies on community resilience?

From a cross-sectional perspective, research has indicated that disasters and emergencies can have a negative effect on certain types of SC. Specifically, cognitive SC has been found to be impacted by disaster impact, whereas structural SC has gone unaffected [ 45 ]. Disaster impact has also been shown to have a negative effect on community relationships more generally [ 52 ].

Additionally, of the eight studies which collected data at multiple time points [ 35 , 36 , 41 , 42 , 47 , 49 , 56 , 60 ], three reported the effect of a disaster on the level of SC within a community [ 40 , 42 , 49 ]. All three of these studies concluded that disasters may have a negative impact on the levels of SC within a community. The first study found that the Deepwater Horizon oil spill had a negative effect on SC and social support, and this in turn explained an overall increase in the levels of depression within the community [ 40 ]. A possible explanation for the negative effect lays in ‘corrosive communities’, known for increased social conflict and reduced social support, that are sometimes created following oil spills [ 40 ]. It is proposed that corrosive communities often emerge due to a loss of natural resources that bring social groups together (e.g., for recreational activities), as well as social disparity (e.g., due to unequal distribution of economic impact) becoming apparent in the community following disaster [ 40 ]. The second study found that SC (in the form of social cohesion, informal socialising and social participation) decreased after the 2011 earthquake and tsunami in Japan; it was suggested that this change correlated with incidence of cognitive decline [ 42 ]. However, the third study reported more mixed effects based on physical circumstances of the communities’ natural environment: Following an earthquake, those who lived in mountainous areas with an initial high level of pre-community SC saw a decrease in SC post disaster [ 49 ]. However, communities in flat areas (which were home to younger residents and had a higher population density) saw an increase in SC [ 49 ]. It was proposed that this difference could be due to the need for those who lived in mountainous areas to seek prolonged refuge due to subsequent landslides [ 49 ].

What types of intervention enhance CR and SC and protect survivors?

There were mixed effects across the 26 retained papers when examining the effect of CR and SC on mental wellbeing. However, there is evidence that an increase in SC [ 56 , 57 ], with a focus on cognitive SC [ 57 ], namely by: building social networks [ 45 , 51 , 53 ], enhancing feelings of social cohesion [ 35 , 36 ] and promoting a sense of community [ 53 ], can result in an increase in CR and potentially protect survivors’ wellbeing and mental health following a disaster. An increase in SC may also aid in decreasing the need for individual psychological interventions in the aftermath of a disaster [ 55 ]. As a result, recommendations and suggested methods to bolster CR and SC from the retained papers have been extracted and separated into general methods, preparedness and policy level implementation.

General methods

Suggested methods to build SC included organising recreational activity-based groups [ 44 ] to broaden [ 51 , 53 ] and preserve current social networks [ 42 ], introducing initiatives to increase social cohesion and trust [ 51 ], and volunteering to increase the number of social ties between residents [ 59 ]. Research also notes that it is important to take a ‘no one left behind approach’ when organising recreational and social community events, as failure to do so could induce feelings of isolation for some members of the community [ 49 ]. Furthermore, gender differences should also be considered as research indicates that males and females may react differently to community level SC (as evidence suggests males are instead more impacted by individual level SC; in comparison to women who have larger and more diverse social networks [ 49 ]). Therefore, interventions which aim to raise community level social participation, with the aim of expanding social connections and gaining support, may be beneficial [ 42 , 47 ].

Preparedness

In order to prepare for disasters, it may be beneficial to introduce community-targeted methods or interventions to increase levels of SC and CR as these may aid in ameliorating the consequences of a public health emergency or disaster [ 57 ]. To indicate which communities have low levels of SC, one study suggests implementing a 3-item scale of social cohesion to map areas and target interventions [ 42 ].

It is important to consider that communities with a high level of SC may have a lower level of risk perception, due to the established connections and supportive network they have with those around them [ 61 ]. However, for the purpose of preparedness, this is not ideal as perception of risk is a key factor when seeking to encourage behavioural adherence. This could be overcome by introducing communication strategies which emphasise the necessity of social support, but also highlights the need for additional measures to reduce residual risk [ 59 ]. Furthermore, support in the form of financial assistance to foster current community initiatives may prove beneficial to rural areas, for example through the use of an asset-based community development framework [ 52 ].

Policy level

At a policy level, the included papers suggest a range of ways that CR and SC could be bolstered and used. These include: providing financial support for community initiatives and collective coping strategies, (e.g. using asset-based community development [ 52 ]); ensuring policies for long-term recovery focus on community sustainable development (e.g. community festival and community centre activities) [ 44 ]; and development of a network amongst cooperative corporations formed for reconstruction and to organise self-help recovery sessions among residents of adjacent areas [ 58 ].

This scoping review sought to synthesise literature concerning the role of SC and CR during public health emergencies and disasters. Specifically, in this review we have examined: the methods used to measure CR and SC; the impact of CR and SC on mental wellbeing during disasters and emergencies; the impact of disasters and emergencies on CR and SC; and the types of interventions which can be used to enhance CR. To do this, data was extracted from 26 peer-reviewed journal articles. From this synthesis, several key themes have been identified, which can be used to develop guidelines and recommendations for deploying CR and SC in a public health emergency or disaster context. These key themes and resulting recommendations are summarised below.

Firstly, this review established that there is no consistent or standardised approach to measuring CR or SC within the general population. This finding is consistent with a review conducted by the World Health Organization which concludes that despite there being a number of frameworks that contain indicators across different determinants of health, there is a lack of consensus on priority areas for measurement and no widely accepted indicator [ 27 ]. As a result, there are many measures of CR and SC apparent within the literature (e.g., [ 62 , 63 ]), an example of a developed and validated measure is provided by Sherrieb, Norris and Galea [ 64 ]. Similarly, the definitions of CR and SC differ widely between researchers, which created a barrier to comparing and summarising information. Therefore, future research could seek to compare various interpretations of CR and to identify any overlapping concepts. However, a previous systemic review conducted by Patel et al. (2017) concludes that there are nine core elements of CR (local knowledge, community networks and relationships, communication, health, governance and leadership, resources, economic investment, preparedness, and mental outlook), with 19 further sub-elements therein [ 30 ]. Therefore, as CR is a multi-dimensional construct, the implications from the findings are that multiple aspects of social infrastructure may need to be considered.

Secondly, our synthesis of research concerning the role of CR and SC for ensuring mental health and wellbeing during, or following, a public health emergency or disaster revealed mixed effects. Much of the research indicates either a generally protective effect on mental health and wellbeing, or no effect; however, the literature demonstrates some potential for a high level of CR/SC to backfire and result in a negative effect for populations during, or following, a public health emergency or disaster. Considered together, our synthesis indicates that cognitive SC is the only facet of SC which was perceived as universally protective across all retained papers. This is consistent with a systematic review which also concludes that: (a) community level cognitive SC is associated with a lower risk of common mental disorders, while; (b) community level structural SC had inconsistent effects [ 65 ].

Further examination of additional data extracted from studies which found that CR/SC had a negative effect on mental health and wellbeing revealed no commonalities that might explain these effects (Please see Supplementary file 5 for additional information)

One potential explanation may come from a retained paper which found that high levels of SC result in an increase in stress level immediately post disaster [ 41 ]. This was suggested to be due to individuals having greater burdens due to wishing to help and support their wide networks as well as themselves. However, as time passes the levels of SC allow the community to come together and recover at a faster rate [ 41 ]. As this was the only retained paper which produced this finding, it would be beneficial for future research to examine boundary conditions for the positive effects of CR/SC; that is, to explore circumstances under which CR/SC may be more likely to put communities at greater risk. This further research should also include additional longitudinal research to validate the conclusions drawn by [ 41 ] as resilience is a dynamic process of adaption.

Thirdly, disasters and emergencies were generally found to have a negative effect on levels of SC. One retained paper found a mixed effect of SC in relation to an earthquake, however this paper separated participants by area in which they lived (i.e., mountainous vs. flat), which explains this inconsistent effect [ 49 ]. Dangerous areas (i.e. mountainous) saw a decrease in community SC in comparison to safer areas following the earthquake (an effect the authors attributed to the need to seek prolonged refuge), whereas participants from the safer areas (which are home to younger residents with a higher population density) saw an increase in SC [ 49 ]. This is consistent with the idea that being able to participate socially is a key element of SC [ 12 ]. Overall, however, this was the only retained paper which produced a variable finding in relation to the effect of disaster on levels of CR/SC.

Finally, research identified through our synthesis promotes the idea of bolstering SC (particularly cognitive SC) and cohesion in communities likely to be affected by disaster to improve levels of CR. This finding provides further understanding of the relationship between CR and SC; an association that has been reported in various articles seeking to provide conceptual frameworks (e.g., [ 66 , 67 ]) as well as indicator/measurement frameworks [ 27 ]. Therefore, this could be done by creating and promoting initiatives which foster SC and create bonds within the community. Papers included in the current review suggest that recreational-based activity groups and volunteering are potential methods for fostering SC and creating community bonds [ 44 , 51 , 59 ]. Similarly, further research demonstrates that feelings of social cohesion are enhanced by general social activities (e.g. fairs and parades [ 18 ]). Also, actively encouraging activities, programs and interventions which enhance connectedness and SC have been reported to be desirable to increase CR [ 68 ]. This suggestion is supported by a recent scoping review of literature [ 67 ] examined community champion approaches for the COVID-19 pandemic response and recovery and established that creating and promoting SC focused initiatives within the community during pandemic response is highly beneficial [ 67 ]. In terms of preparedness, research states that it may be beneficial for levels of SC and CR in communities at risk to be assessed, to allow targeted interventions where the population may be at most risk following an incident [ 42 , 44 ]. Additionally, from a more critical perspective, we acknowledge that ‘resilience’ can often be perceived as a focus on individual capacity to adapt to adversity rather than changing or mitigating the causes of adverse conditions [ 69 , 70 ]. Therefore, CR requires an integrated system approach across individual, community and structural levels [ 17 ]. Also, it is important that community members are engaged in defining and agreeing how community resilience is measured [ 27 ] rather than it being imposed by system leads or decision-makers.

In the aftermath of the pandemic, is it expected that there will be long-term repercussions both from an economic [ 8 ] and a mental health perspective [ 71 ]. Furthermore, the findings from this review suggest that although those in areas with high levels of SC may be negatively affected in the acute stage, as time passes, they have potential to rebound at a faster rate than those with lower levels of SC. Ongoing evaluation of the effectiveness of current initiatives as the COVID-19 pandemic progresses into a recovery phase will be invaluable for supplementing the evidence base identified through this review.

• Recommendations

As a result of this review, a number of recommendations are suggested for policy and practice during public health emergencies and recovery.

Future research should seek to establish a standardised and validated approach to measuring and defining CR and SC within communities. There are ongoing efforts in this area, for example [ 72 ]. Additionally, community members should be involved in the process of defining how CR is measured.

There should be an enhanced effort to improve preparedness for public health emergencies and disasters in local communities by gauging current levels of SC and CR within communities using a standardised measure. This approach could support specific targeting of populations with low levels of CR/SC in case of a disaster or public health emergency, whilst also allowing for consideration of support for those with high levels of CR (as these populations can be heavily impacted initially following a disaster). By distinguishing levels of SC and CR, tailored community-centred approaches could be implemented, such as those listed in a guide released by PHE in 2015 [ 73 ].

CR and SC (specifically cognitive SC) should be bolstered if communities are at risk of experiencing a disaster or public health emergency. This can be achieved by using interventions which aim to increase a sense of community and create new social ties (e.g., recreational group activities, volunteering). Additionally, when aiming to achieve this, it is important to be mindful of the risk of increased levels of CR/SC to backfire, as well as seeking to advocate an integrated system approach across individual, community and structural levels.

It is necessary to be aware that although communities with high existing levels of resilience / SC may experience short-term negative consequences following a disaster, over time these communities might be able to recover at a faster rate. It is therefore important to ensure that suitable short-term support is provided to these communities in the immediate aftermath of a public health emergency or disaster.

Robust evaluation of the community resilience initiatives deployed during the COVID-19 pandemic response is essential to inform the evidence base concerning the effectiveness of CR/ SC. These evaluations should continue through the response phase and into the recovery phase to help develop our understanding of the long-term consequences of such interventions.

Limitations

Despite this review being the first in this specific topic area, there are limitations that must be considered. Firstly, it is necessary to note that communities are generally highly diverse and the term ‘community’ in academic literature is a subject of much debate (see: [ 74 ]), therefore this must be considered when comparing and collating research involving communities. Additionally, the measures of CR and SC differ substantially across research, including across the 26 retained papers used in the current review. This makes the act of comparing and collating research findings very difficult. This issue is highlighted as a key outcome from this review, and suggestions for how to overcome this in future research are provided. Additionally, we acknowledge that there will be a relationship between CR & SC even where studies measure only at individual or community level. A review [ 75 ] on articulating a hypothesis of the link to health inequalities suggests that wider structural determinants of health need to be accounted for. Secondly, despite the final search strategy encompassing terms for both CR and SC, only one retained paper directly measured CR; thus, making the research findings more relevant to SC. Future research could seek to focus on CR to allow for a comparison of findings. Thirdly, the review was conducted early in the COVID-19 pandemic and so does not include more recent publications focusing on resilience specifically in the context of COVID-19. Regardless of this fact, the synthesis of, and recommendations drawn from, the reviewed studies are agnostic to time and specific incident and contain critical elements necessary to address as the pandemic moves from response to recovery. Further research should review the effectiveness of specific interventions during the COVID-19 pandemic for collation in a subsequent update to this current paper. Fourthly, the current review synthesises findings from countries with individualistic and collectivistic cultures, which may account for some variation in the findings. Lastly, despite choosing a scoping review method for ease of synthesising a wide literature base for use by public health emergency researchers in a relatively tight timeframe, there are disadvantages of a scoping review approach to consider: (1) quality appraisal of retained studies was not carried out; (2) due to the broad nature of a scoping review, more refined and targeted reviews of literature (e.g., systematic reviews) may be able to provide more detailed research outcomes. Therefore, future research should seek to use alternative methods (e.g., empirical research, systematic reviews of literature) to add to the evidence base on CR and SC impact and use in public health practice.

This review sought to establish: (1) How CR and SC are quantified in research?; (2) The impact of community resilience on mental wellbeing?; (3) The impact of infectious disease outbreaks, disasters and emergencies on community resilience and social capital?; and, (4) What types of interventions enhance community resilience and social capital?. The chosen search strategy yielded 26 relevant papers from which we were able extract information relating to the aims of this review.

Results from the review revealed that CR and SC are not measured consistently across research. The impact of CR / SC on mental health and wellbeing during emergencies and disasters is mixed (with some potential for backlash), however the literature does identify cognitive SC as particularly protective. Although only a small number of papers compared CR or SC before and after a disaster, the findings were relatively consistent: SC or CR is negatively impacted by a disaster. Methods suggested to bolster SC in communities were centred around social activities, such as recreational group activities and volunteering. Recommendations for both research and practice (with a particular focus on the ongoing COVID-19 pandemic) are also presented.

Availability of data and materials

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Abbreviations

Social Capital

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This study was supported by the National Institute for Health Research Research Unit (NIHR HPRU) in Emergency Preparedness and Response, a partnership between Public Health England, King’s College London and the University of East Anglia. The views expressed are those of the author(s) and not necessarily those of the NIHR, Public Health England, the UK Health Security Agency or the Department of Health and Social Care [Grant number: NIHR20008900]. Part of this work has been funded by the Office for Health Improvement and Disparities, Department of Health and Social Care, as part of a Collaborative Agreement with Leeds Beckett University.

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DW, JSo and JSt had the main idea for the review. The search strategy and eligibility criteria were devised by CH, DW, JSo and JSt. CH conducted the database searches. CH and DW conducted duplicate, title and abstract and full text screening in accordance with inclusion criteria. CH conducted data extraction, CH and DW carried out the analysis and drafted the initial manuscript. All authors provided critical revision of intellectual content. All authors approved the final manuscript.

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Hall, C.E., Wehling, H., Stansfield, J. et al. Examining the role of community resilience and social capital on mental health in public health emergency and disaster response: a scoping review. BMC Public Health 23 , 2482 (2023). https://doi.org/10.1186/s12889-023-17242-x

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A survey on spatio-temporal series prediction with deep learning: taxonomy, applications, and future directions

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• Feiyan Sun 1 , 2 ,
• Wenning Hao   ORCID: orcid.org/0000-0002-1526-7889 1 ,
• Ao Zou 1 &
• Qianyan Shen 2  

With the rapid development of data acquisition and storage technology, spatio-temporal (ST) data in various fields are growing explosively, so many ST prediction methods have emerged. The review presented in this paper mainly studies the prediction of ST series. We propose a new taxonomy organized along three dimensions: ST series prediction methods (focusing on time feature learning, focusing on spatial feature learning, and focusing on spatial–temporal feature learning), techniques of ST series prediction (the RNN-, CNN-, and transformer-based models, as well as the CNN-based-composite model and GNN-based-composite models, and the miscellaneous model) and ST series prediction results (single target and multi-target). We first introduce and explain each dimension of the taxonomy in detail. After providing this three-dimensional view, we comprehensively review and compare the recent related ideas in the literature and analyze their advantages and limitations. Moreover, we summarize the key information of the existing literature and provide guidance for researchers to select suitable models. Second, we summarize the different applications of deep learning models in ST series prediction based on current literature and list relevant datasets and download links per application classifications. Lastly, we comprehensively analyze the current innovation and challenges and suggest future directions for researching ST series prediction after comparing and analyzing the computing performance of these forecasting models. In addition, each method or model solves one aspect of the challenge, which means that two or more methods should be combined to solve more challenges at the same time. We hope this article provides readers a broader and deeper understanding of the field of ST series research.

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Acknowledgements

This research is supported by Defense Industrial Technology Development Program, Grant/Award Number: JCKY2020601B018; Research Fund of Jinling Institute of Technology for Advanced Talents, Grant/Award Number: jit-b-201805. The authors would like to thank Haijun Zhang, the associate editor of Neural Computing and Applications, and anonymous reviewers for their insightful comments and suggestions. As a result, this paper has been improved substantially.

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Army Engineering University of PLA, Nanjing, China

Feiyan Sun, Wenning Hao & Ao Zou

Jinling Institute of Technology, Nanjing, China

Feiyan Sun & Qianyan Shen

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Appendix 1. Methods

See Table 12 .

Appendix 2. Table Note

Here, we provide keys to help read the tables in the paper,

Results means whether the method does single-target predictions and predicts multi-target simultaneously.

Loss and metrics indicates the loss of training and metrics of evaluation. Because the definitions can be found in relevant papers, we provide only explanations of abbreviations here: mean absolute error (MAE), mean relative error (MRE), mean absolute percentage error (MAPE), normalized root mean squared error (NRMSE, RMSE, MSE), L1 loss (MAE), L2 loss (MSE), quantile loss (QL), empirical correlation coefficient (CORR), root relative squared error (RRSE), negative log-likelihood (NLL), ρ-quantile loss R_ρ with ρϵ(0,1), and symmetric mean absolute percentage error (sMAPE).

Structure refers to the different combinations of time and spatial modeling, including series, parallel, and fusion structures. Series structure models one dimension first, using the output obtained as input for modeling another dimension, and then models the other dimension. One example is modeling the temporal dependency relationship of input features first, using the resulting output as input to the spatial relationship extraction module, conducting spatial modeling, and finally obtaining the final predicted value. Parallel structure means the input sequence is simultaneously input into both the time and spatial networks for learning temporal and spatial dependencies. The obtained time and spatial network information are fused before being applied as the input sequence to the next layer. After an intervention round, further learning is done to obtain the final prediction result. Fusion structure refers to time modeling and spatial modeling that are not independent but cross-integrated, for example, when time modeling is conducted, each time step incorporates the spatial information of the nodes rather than simply their own time series.

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Sun, F., Hao, W., Zou, A. et al. A survey on spatio-temporal series prediction with deep learning: taxonomy, applications, and future directions. Neural Comput & Applic (2024). https://doi.org/10.1007/s00521-024-09659-1

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Reversing frailty in older adults: a scoping review

• Aurélie Tonjock Kolle 1 ,
• Krystina B. Lewis 1 , 2 , 3 ,
• Michelle Lalonde 1 , 4 &
• Chantal Backman 1 , 2 , 5  

BMC Geriatrics volume  23 , Article number:  751 ( 2023 ) Cite this article

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Individuals 65 years or older are presumably more susceptible to becoming frail, which increases their risk of multiple adverse health outcomes. Reversing frailty has received recent attention; however, little is understood about what it means and how to achieve it. Thus, the purpose of this scoping review is to synthesize the evidence regarding the impact of frail-related interventions on older adults living with frailty, identify what interventions resulted in frailty reversal and clarify the concept of reverse frailty.

We followed Arksey and O’Malley’s five-stage scoping review approach and conducted searches in CINAHL, EMBASE, PubMed, and Web of Science. We hand-searched the reference list of included studies and conducted a grey literature search. Two independent reviewers completed the title, abstract screenings, and full-text review using the eligibility criteria, and independently extracted approximately 10% of the studies. We critically appraised studies using Joanna Briggs critical appraisal checklist/tool, and we used a descriptive and narrative method to synthesize and analyze data.

Of 7499 articles, thirty met the criteria and three studies were identified in the references of included studies. Seventeen studies (56.7%) framed frailty as a reversible condition, with 11 studies (36.7%) selecting it as their primary outcome. Reversing frailty varied from either frail to pre-frail, frail to non-frail, and severe to mild frailty. We identified different types of single and multi-component interventions each targeting various domains of frailty. The physical domain was most frequently targeted (n = 32, 97%). Interventions also varied in their frequencies of delivery, intensities, and durations, and targeted participants from different settings, most commonly from community dwellings (n = 23; 69.7%).

Some studies indicated that it is possible to reverse frailty. However, this depended on how the researchers assessed or measured frailty. The current understanding of reverse frailty is a shift from a frail or severely frail state to at least a pre-frail or mildly frail state. To gain further insight into reversing frailty, we recommend a concept analysis. Furthermore, we recommend more primary studies considering the participant’s lived experiences to guide intervention delivery.

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Within the next few decades, the population of people aged 65 and over will continue to rise more than all other age groups, with roughly one in six people over 65 by 2050, compared to one in eleven in 2019 [ 1 ]. Individuals over 65 years are presumably at greater risk of becoming frail [ 2 , 3 , 4 ]. Theoretically, frailty is considered a clinically recognized state of vulnerability that results from an age-related decline in reserve and function, compromising an individual’s ability to cope with the daily challenges of life [ 5 , 6 ]. The Frailty Phenotype (FP), which is the most dominant conceptual model in literature [ 3 , 7 , 8 , 9 , 10 ], considers an individual frail by the presence of at least three of five phenotypes: weakness, low levels of physical activity, unintentional weight loss, slow walking speed, and exhaustion. Physical, cognitive, psychological, and social impairments often characterize the different domains of frailty [ 11 ]. The physical domain is devoted to FP-related conditions [ 12 ], the cognitive domain is the co-existence of physical deficits and mild cognitive impairments [ 13 ], the psychological domain focuses on an individual’s coping mechanisms based on their own experiences [ 14 ], and the social domain looks at a person’s limited participation in social activities and limitations in social support [ 15 ]. Frail older adults are prone to adverse outcomes such as frequent falls, hospitalizations, disabilities, loneliness, cognitive decline, depression, poor quality of life, and even death [ 16 , 17 , 18 ]. In response, researchers have proposed various interventions to prevent or slow frailty progression by either targeting a single domain (e.g., physical, social, cognitive, etc.) using single component interventions or targeting two or more domains using multi-component interventions.

For example, Hergott and colleagues investigated the effects of a single-component intervention, functional exercise, on acromegaly-induced frailty [ 19 ]. Abizanda and colleagues examined the effects of a multi-component intervention, composed of nutrition and physical activity, on frail older people’s physical function and quality of life [ 20 ]. Some studies indicate that certain single or multi-component interventions can either reduce frailty, slow its progression, and possibly reverse it [ 3 , 21 , 22 ]. The current understanding of reverse frailty lacks clarity, and the characteristics of interventions related to frailty reversal have not yet been examined in a systematic manner.

Authors have determined the reversal of frailty using various measures. For instance, Kim and colleagues’ study evaluating an intervention composed of exercise and nutritional supplementation in frail elderly community-dwellers demonstrated reversals in FP components [ 23 ]. Components included fatigue, low physical activity, and slow walking, an improvement from the presence of 5 components of frailty (according to the FP) to 2, considered a pre-frail state [ 23 ]. Conversely, De Souto and colleagues demonstrated frailty reversal based on changes in frailty index (FI) scores, a measure of accumulation of deficits [ 24 ]. A FI score of 0.22 or greater indicates frailty, score less than or equal to 0.10 indicates a non-frail state [ 25 , 26 , 27 , 28 , 29 ]. Hergott et al. (2020) used frailty severity to indicate frailty reversal. Participants in their study reversed frailty from a severe state to a mild state [ 19 ]. These studies demonstrate the variability in how reversing frailty is measured and understood. For a more comprehensive understanding of reverse frailty and the characteristics of interventions associated with it, a comprehensive review of the literature on this topic is needed. Therefore, through a scoping review, the aim of this study is to provide an overview and synthesis of interventions that have been implemented for frail older adults, to determine whether some interventions have had an impact on reversing frailty.

This methodology is ideal because it encompasses a broad scope and can comprehensively analyze and synthesize data on a subject [ 30 ]. Findings from this review will synthesize the evidence regarding the impact of frail-related interventions on older adults living with frailty, identify what interventions resulted in frailty reversal and clarify the concept of reverse frailty.

Guiding conceptual framework

The deficit accumulation model framework, unlike the FP, considers frailty as more than a physical deficit but rather an accumulation of health-related deficits across multiple domains [ 31 ]. For this reason, the deficit accumulation model framework serves as our guiding conceptual framework. Through this framework, we recognize frailty as a complex phenomenon, strengthening the case for interventions addressing other health and personal concerns, such as illness, environmental disturbance, social dysfunction, cognitive decline, and psychosocial distress. This framework provides a helpful lens through which we can examine the number of domains addressed in the reported interventions and their relationship to one another.

We followed Arksey and O’Malley’s [ 30 ] five-stage approach, elaborated by Levac et al., [ 32 ] and Joanna Briggs Institute (JBI) for scoping review [ 33 ]. They propose six stages: (1) identifying the research question, (2) locating relevant studies, (3) selecting the study, (4) charting data, (5) summarizing results, and (6) consulting with stakeholders. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes Extension for Scoping Reviews (PRISMA-ScR) checklist [ 34 ] to guide study reporting. Refer to Additional file 1 .

Stage one: identifying the research question

According to Levac and colleagues, fundamental research questions should be broad enough to enable comprehensive analysis and appropriate mapping of relevant literature [ 32 ]. Following this, our three research questions are as follows:

What is the available literature on the impact of interventions for frail older adults?

Did any of these interventions result in frailty reversal?

What does it mean to reverse frailty?

Stage two: identifying relevant studies

Using the research questions as a guide, we engaged in an iterative process that involved searching the literature, identifying search terms, developing, and refining search strategies, to identify appropriate studies. We also sought the assistance of an experienced librarian who gave guidance on the use of various electronic databases, provided validation on the appropriateness of the methodology for this study, and conducted a peer-review of the search strategies. An overview of each step is provided below.

Eligibility criteria

JBI’s PCC mnemonic guided eligibility criteria, where P (population): frail older people over 65yrs of age, C (concept): frailty outcome, and C (context): all contexts. We included French and English studies of frail older adults over 65 years because most studies focused on frailty target this age group [ 35 , 36 , 37 , 38 ]. All types of interventions for frail older adults were included, except for interventions intended to prevent frailty. We did not apply any limitations to study dates, and settings. All study designs (quantitative, qualitative, and mixed methods) were considered for inclusion. We excluded conference abstracts, theses, dissertations, and knowledge syntheses, but did refer to their reference list for potential studies. Lastly, we performed a grey literature scan to identify relevant primary studies to ensure a comprehensive literature search.

Search terms

An a priori concept analysis [ 39 ] of frailty and frailty interventions revealed relevant search terms regarding the population of interest which included ‘frail elderly, frail, aged hospital patient, institutionalized elderly, very elderly, geriatrics, senior, and aged’. These keywords were presented to and approved by an academic librarian (VL). To capture a comprehensive list of studies that may be relevant, we looked at all types of interventions on frail older adults aimed at either reducing, improving, managing, enhancing, treating, or reversing frailty. Medical Subject Headings (MeSH) and boolean operators of these terms were used in different databases to identify relevant studies.

Search strategy

Two academic librarians (VL & VC) guided the development of the search strategy and selected databases. We conducted the searches between August 6th and August 9th, 2021, using MEDLINE (OVID interface), Embase (OVID interface), Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Web of Science. We first implemented the search in MEDLINE (Fig.  1 ), which we later adapted for the other three databases. We manually searched for relevant studies from the reference lists of included/eligible articles and reviewed conference abstracts and secondary analyzes to identify primary studies. A third academic librarian (LS) peer-reviewed the search strategy using the Peer Review of Electronic Search Strategies (PRESS) guidelines [ 40 ] on August 19th, 2021, without modification. On August 23rd, 2021, we imported the results in RIS format into Covidence, a web-based system for systematic reviews provided by Cochrane [ 41 , 42 ], which also removed duplicates. We did not import the articles identified via hand-searching the reference list into Covidence for screening. However, two reviewers independently assessed the articles’ eligibility according to our eligibility criteria.

Ovid MEDLINE search strategy

Stage three: study selection

There were two reviewers (AK, OB) involved in this stage, which involved a first and second screening level. The first level included an independent screening of the titles and abstracts, and we decided by selecting ‘yes’, ‘no’, or ‘maybe’. To qualify for full-text screening, a study must receive two ‘yes’ or two ‘maybe’ votes. Two ‘no’ votes moved the study to exclude, and one ‘no’ vote along with one ‘yes’ or ‘maybe’ vote moved it to conflicts, pending resolution. After consultation with the second reviewer, the first author (AK) and second reviewer (OB) resolved the conflicts together. Following this first-level screen, the second level involved a full-text review of all studies included at the title-abstract level. Using the same principles as the first level screening, the first author (AK) and another reviewer (MA) completed this stage [ 41 , 42 ]. In cases where full-text articles could not be located or had to be purchased, the corresponding authors were contacted once by email to request copies. We excluded the articles if we did not receive a response after two weeks. We also searched Google Scholar for conference abstracts to see if the full text of the papers had been published and accessible. For most searches, this process was ineffective, leading to the exclusion of all conference abstracts. Articles excluded with reasons can be found in Additional file 2 .

Stage Four: charting the data

To extract essential information from the articles, we developed a standard Microsoft Excel form a priori. We used the Template for Intervention Description and Replication (TIDieR) checklist [ 43 ] to guide the extraction of the interventions. The form was pilot tested with five articles and revised following recommendations from the research team. After establishing the information to be extracted, we imported the data into Google Forms to facilitate the extracting process for the reviewers. To ensure consistency and reliability in data extraction, two reviewers (AK and MA) independently extracted data from at least 10% of the included studies and compared the results, as recommended by Levac and colleagues [ 32 ]. Once we established consistency, the first author (AK) extracted data from the remaining studies.

Data extracted

Data extraction items include a bibliography (authors, the journal-title and year of publication), setting, study population (frail, number and age of participants), aims of the study, the conceptual framework of frailty used, domains of frailty considered, details on interventions that reduce, enhance, treat or reverse frailty, the framework used to develop interventions, assessment tools or instruments to assess frailty outcome before and/or after the intervention, outcomes (frailty completely, partially, or not reversed). Data extraction items can be found in Additional file 3 .

Quality appraisal (QA)

We critically appraised included studies strengths and limitations of the studies (e.g., randomized controlled trials, quasi-experimental studies, case reports, case series, and cohort studies) using the corresponding JBI checklist for quality appraisal. Checklists, ranged from eight to 13 items [ 35 ]. Answers to the questions in each scale ranged from ‘yes’, ‘no’, and ‘unclear’. Three reviewers (YA, MA, and AK) independently appraised the included studies. After completing the assessment, the first author (AK) sorted the answers to determine any discrepancies. When two reviewers reported the same answer, agreement was achieved. When answers differed, the first author extensively reviewed the study and discussed the differences with the other two to reach a consensus. After completion, we converted all the answers into descriptive variables, with yes representing ‘1’ and no and unclear meaning ‘0’. Following recommendations from some studies [ 44 , 45 ], we used these variables to generate a total score, which we further used to classify a study into “low”, “moderate”, and “high” risk of bias. The quality appraisal interpretation scale can be found in Additional file 4 .

Stage five: summarizing and reporting the results

Data analysis.

To summarize and elaborate on the first research question, we used a narrative synthesis. Initially, we developed a preliminary synthesis by grouping studies that focused on similar concepts such as but not limited to types of interventions, domains of frailty targeted, outcome of interventions, into a tabular format. Next, using excel, we created bar graphs where we explored relationships between and within studies. Through the use of conceptual mapping, we linked multiple pieces of evidence from individual studies to highlight key concepts and ideas [ 46 , 47 ].

Our approach to answering the second research question, comparing study demographics and participant characteristics, was descriptive in nature. Using Excel, we calculated the counts and frequencies of variables in each category and compared their percentages across studies [ 48 ].

Study selection

We identified 7499 potential records, of which thirty met eligibility criteria. In addition, our hand search of references of included studies revealed three eligible studies, reaching a total of thirty-three. We illustrate the screening and selection process for the included studies using the PRISMA 2020 flow diagram for systematic reviews (Fig.  2 ).

PRISMA flow diagram of the search process for studies

Study characteristics

Sample sizes ranged from one to 250,428 participants across the studies. The most common study designs were randomized controlled trials (RCTs) (n = 23) [ 22 , 23 , 24 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 ], quasi-experimental (n = 4) [ 69 , 70 , 71 , 72 ], cohort Studies (n = 3) [ 20 , 73 , 74 ], case series (n = 2) [ 75 , 76 ] and a case report (n = 1) [ 19 ]. Geographically, the studies took place in fifteen different countries, namely Japan (n = 6) [ 23 , 49 , 53 , 58 , 72 , 74 ], Spain (n = 6) [ 20 , 59 , 60 , 62 , 70 , 75 ], United States of America (n = 4) [ 19 , 63 , 64 , 68 ], China (n = 3) [ 51 , 52 , 69 ], Sweden (n = 2) [ 50 , 55 ], South Korea (n = 2) [ 71 , 76 ], Singapore (n = 2) [ 22 , 54 ], Australia (n = 1) [ 66 ], Netherlands (n = 1) [ 65 ], Canada (n = 1) [ 73 ], France (n = 1) [ 24 ], Brazil (n = 1) [ 67 ], Thailand (n = 1) [ 56 ], Turkey (n = 1) [ 57 ], Denmark (n = 1) [ 61 ]. Publication dates ranged from June 23rd, 1994, to January 2nd, 2021, with most articles (n = 24) published after 2015.

Critical appraisal results

The quality assessment scores of the studies ranged from seven to twelve, and study bias was low to moderate for all included studies (Appendix 4). Given that scoping reviews do not mandate the inclusion of studies based on critical appraisal results [ 77 ], we did not exclude studies based on their quality assessment cores.

Participant characteristics

Twelve studies (36.4%) included participants over 65 years of age, 11 studies (33.3%) over 70 years of age, and 10 studies (30.3%) over 75 years of age. Most authors referred to participants as male or female without definition making it difficult to distinguish between gender and sex. Consequently, we present the results as reported in the studies. All but one study reported the sex/gender of participants [ 57 ], with one study having only male participants [ 19 ] and two studies having only female participants as per their eligibility criteria [ 23 , 61 ]. In many studies, the presence of comorbidities beyond frailty was not a requirement for participation (n = 27). Some studies, however, required comorbid conditions for inclusion, such as acromegaly (n = 1) [ 19 ], cardiovascular disease (n = 1) [ 72 ], chronic obstructive pulmonary disease/lung disease (n = 1) [ 60 ], fatigue (n = 1) [ 69 ], and risk of mobility disability and sedentary lifestyle (n = 1) [ 64 ]. Table  1 presents a summary of participant characteristics.

Most and least common domains targeted

Twenty-six studies involved intervention and control groups. Additionally, each study’s intervention targeted at least one domain of frailty. For example, some interventions targeted one single domain (n = 23) [ 19 , 20 , 23 , 49 , 50 , 52 , 53 , 55 , 56 , 57 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 67 , 68 , 70 , 72 , 73 , 74 ], two domains (n = 6) [ 4 , 22 , 54 , 56 , 57 , 78 ], three domains (n = 2) [ 58 , 66 ], and four domains of frailty (n = 2) [ 51 , 71 ]. Counts per domain are presented in Fig.  3 . The most targeted domains were the physical and the cognitive domains. The social domain was the least targeted.

Breakdown of the domains identified in studies

Single and multi-component interventions

Thirteen studies (39.4%) focused on single-component interventions; twelve were physical activity interventions [ 52 , 53 , 56 , 60 , 62 , 63 , 64 , 67 , 70 , 73 , 76 ], and one was a social intervention [ 74 ]. These activities were either individually tailored or performed in a group. Over 50% of the studies focused on multicomponent interventions [ 19 , 20 , 22 , 23 , 24 , 49 , 50 , 51 , 54 , 55 , 58 , 59 , 65 , 66 , 68 , 69 , 71 , 72 , 75 ]. The number of components varied across interventions; from two components to the interventions (n = 10) [ 20 , 23 , 49 , 50 , 55 , 59 , 65 , 68 , 69 , 75 ], three components to the interventions (n = 8) [ 19 , 22 , 24 , 54 , 58 , 66 , 71 , 72 ], or four components to the interventions (n = 2) [ 51 , 71 ]. Characteristics of the interventions are.

included in Table  2 .

Most and least common frailty definitions used

Frailty was defined in all but three studies (n = 30) [ 49 , 61 , 68 ]. Two different definitions of frailty were used dominantly: Fried’s phenotype (n = 20) [ 20 , 22 , 23 , 51 , 52 , 53 , 54 , 56 , 57 , 59 , 62 , 64 , 66 , 67 , 69 , 70 , 71 , 72 , 75 , 76 ], and the Frailty Index (n = 4) [ 24 , 60 , 71 , 73 ]. Notwithstanding, other definitions of frailty involved the use of the clinical frailty scale [ 19 ] and checklist such as the kihon checklist [ 74 ].

Studies without frailty reversal outcome

In the 33 studies included, the results of 22 did not indicate reversal of frailty. Among these, 36.36% (n = 8) focused solely on physical interventions [ 53 , 57 , 60 , 61 , 62 , 63 , 64 , 76 ], while 63.63% (n = 14) combined physical activity with nutritional, cognitive, social, pharmaceutical, or behavioral interventions [ 20 , 24 , 49 , 50 , 51 , 54 , 55 , 58 , 65 , 66 , 68 , 69 , 71 , 75 ]. Although physical activity remains a significant factor in these studies, the types of physical activity (aerobic, strengthening, gait, resistance, etc.) varied. Research suggests that resistance exercise performed at high intensity over a minimum of 12 weeks has the most beneficial effect on physical frailty [ 68 , 79 ]. When done regularly over the course of six months, it has the potential to improve both the physical and physiological aspects of frailty [ 80 ]. In this context, we noted that resistance exercise was more prevalent than other forms of physical activity. Although similar physical activities were often implemented, their characteristics often differed. For example, there was variation in frequency from daily to three times per week, variation in intensity from moderate to high, and variation in duration from 6 weeks to 6 months.

In addition to physical activity, other types of interventions were also used, including cognitive interventions such as memory and reasoning training, pharmaceutical interventions such as medication reconciliation, social interventions such as improving social lifestyles, and behavioral interventions such as goal setting, action plans, and goal execution. Similarly, the characteristics of these interventions were heterogeneous across studies, with some provided as group therapies, and others designed as per the needs of participants.

Studies indicating frailty reversal outcome

Eleven studies reported frailty reversal as an outcome [ 19 , 22 , 52 , 56 , 59 , 67 , 70 , 72 , 73 , 74 , 81 ]. The physical domain was targeted in over 80% of the studies (n = 9) [ 19 , 23 , 52 , 56 , 59 , 67 , 70 , 72 , 73 ], while the social [ 74 ] and cognitive domains [ 22 ] were each targeted in one study. In single-component interventions such as physical activities (n = 5) [ 52 , 56 , 67 , 70 , 73 ], resistance exercises appeared to be the most common, done on its own or in combination with other physical exercises. Meanwhile, the social intervention enhanced the patient’s social capital, a social network that facilitates access to benefits and helps individuals solve problems through association [ 74 ].

The multi-component intervention consisted of physical activity combined with either nutritional counselling/advice or supplements. Some (n = 5) of the interventions included physical activity, nutrition, plus pharmaceutical intervention in one study [ 72 ], physical activity, nutritional plus cognitive intervention in another study [ 22 ], and physical activity combined with occupational and speech therapy [ 19 ], with intervention characteristics varying across studies.

Definition/clarity about the concept of reverse frailty

Authors of 17 studies referred to frailty as a reversible condition. However, the concept of reversing frailty was not defined or explained in six studies [ 22 , 54 , 57 , 58 , 63 , 64 ]. When defined, definitions varied. Some authors defined it as a shift from a frail to pre-frail state (n = 1) [ 56 ], frail to non-frail (n = 2) [ 24 , 59 ], frail to pre- and non-frail (7) [ 23 , 52 , 67 , 70 , 72 , 73 , 74 ], and severe frailty to mild frailty (n = 1) [ 19 ]. What was common across all definitions is that the direction of reversal was from a more severe state of frailty to a less severe state of frailty or pre-frail state. What is different is the degree of frailty, given that some definitions indicated a participant should be frail while others indicated participants being severely frail. This suggests the use of different definitions, criteria, methods, and measures to determine whether frailty reversal occurred. For example, seven of the studies that showed reversal used the definition of Fried et al., [ 23 , 52 , 56 , 59 , 67 , 70 , 72 ], one study used the frailty index [ 73 ], and another study used the clinical frailty scale [ 19 ]. Finally, one study used the Kihon checklist, consisting of 25 yes or no questions on daily-life-related activities, motor functions, nutritional status, oral functions, homebound, cognitive functions, and depressed mood [ 74 ].

Our study aimed to summarize and synthesize evidence on the impact of interventions on frail older adults, to identify those that resulted in frailty reversal and those that did not. In cases where frailty reversal was indicated, we explored the meaning of the concept of reversing frailty. Among the 33 studies included, frailty was revealed to be a complex syndrome encompassing multiple domains, indicating the need for interventions targeting different aspects. Even though some interventions were more prevalent, we observed similarities between types of interventions across studies that showed frailty reversal and those that did not. We noted that the physical domain received the most attention across all studies, whereas the social domain received the least attention in studies with frailty reversal outcomes. Considering that frailty has been defined, addressed, or assessed in multiple ways throughout the studies, further exploration will contribute to clarifying the concept of reversing frailty. These findings lead us to the following points.

Frailty reversal may depend on targeted domains

To the best of our knowledge, the present study is the first to systematically map interventions that indicate frailty reversal as an outcome and relates these interventions to the targeted frailty domains. Using the deficit accumulation model framework as our conceptual framework, we anticipated interventions would target multiple domains of frailty to achieve frailty reversal. However, this was not the case. We identified that the physical domain of frailty is the most frequently targeted as compared to the cognitive, social, and psychological domains. This is supported by the findings of other reviews where authors perceived frailty as primarily a physical impairment, measured by the Fried criteria [ 82 , 83 , 84 , 85 , 86 , 87 ]. This finding suggests that reversing frailty may probably depend on the domain that is targeted by the intervention, or the conceptual framework used to identify and measure its outcome.

Definition of reverse frailty remains unclear

There is no standard definition of reverse frailty, yet the concept appears in several research studies. We used a descriptive approach such as percentages to examine the differences and similarities between the various definitions. A fundamental similarity is that the individual must be deemed frail at baseline. However, the process of determining an individual’s frailty score or status differed among the studies because of the different assessment instruments used. Another similarity was that to reverse frailty, frailty scores or status must not progress to a more severe state but rather improve to a pre-frail or milder state of frailty. Further research is required to clarify this concept, preferably through concept analysis.

Absence of a universal method to reverse frailty

This review included a heterogeneous group of studies with a diverse range of participant characteristics, intervention types, and duration of intervention. Single-component and multi-component interventions have shown efficacy in reversing frailty, with more studies of single-component interventions (i.e., physical activity or social interventions) than the latter.

Use of single-component interventions to reverse frailty

Our study identified physical activity as the most used intervention across studies that reversed frailty. This fits with previous findings that physical activity is essential in interventions for frail older adults [ 85 , 86 , 87 , 88 ]. The activities were performed together (combination exercises) or separately (resistance only). In one study, frailty was reversed as early as six weeks [ 70 ]. The authors attributed this to the combination of resistance, strength training and aerobic exercises. Therefore, when combined with other types of exercise, resistance exercise could promote the rapid improvement of physical frailty.

According to a recent scoping review, social frailty has not received adequate attention [ 15 ]. Based on the findings of our review, we agree with this notion, given we identified only one study [ 74 ] that explored frailty reversal through singular intervention. Using an established checklist of items, the study monitored the effects of enhanced social capital (including interaction with neighbours, trust in the community, social participation in activities) on frailty reversal over two years. The results showed that 31.8% of the participants’ frailty statuses reversed to pre-frail or non-frail Another study [ 58 ] showed that increasing participants’ social capital improved their adherence to activities and encouraged them to continue interventions even after the study had ended. Thus, interventions that consider this approach may have better outcomes when it comes to frailty reversal.

Use of multi-component interventions to reverse frailty

The studies(n = 11) that showed frailty reversal as an outcome employed a combination of two or more intervention components tailored to participant needs or conducted in small groups. Physical activity, particularly resistance exercise, is recommended in conjunction with nutritional interventions as a preventative measure of muscle atrophy in older adults [ 58 ], which may explain why this combination was the most common among the multi-component interventions. We also noted other physical activities such as strength, balance gait and aerobic exercise performed in combination with resistance exercise at varying frequencies and durations. Nutritional interventions included dietary supplements and nutritional education (advice and counselling) on healthy food choices, with the latter being the most reportedly used. We related the advantage of this approach as reported in other studies where Interventions that aimed to empower participants by way of soliciting and incorporating their input (e.g., choosing meals) were more likely to result in participants feeling in control and autonomous over their dietary choices [ 89 , 90 ]. This may explain how nutritional education may provide older adults with more food variety and improved food intake compared with dietary supplements [ 58 ]. In addition to nutritional education and physical activity, Ushijima et al. [ 72 ] also provided medication guidance, to mitigate the effects of polypharmacy, which have been shown to negate the effects of physical and nutritional interventions [ 91 , 92 ].

Recommendations

The results and discussion points above guide our research, practice, and policy recommendations.

In this scoping review, the reporting of the interventions was suboptimal. For example, not all studies reported whether interventions were modified, personalization of interventions were planned, fidelity and adherence were measured, or how intervention fidelity was maintained or improved. Therefore, we recommend that authors use the template for intervention description and replication (TIDIER) checklist [ 43 ] or the Standards for Reporting Implementation Studies (StaRI) [ 93 ] whenever possible to improve intervention reporting. These checklists facilitate clinician use of interventions and researchers’ synthesis and replication. Additionally, we recommend that authors of future studies provide details on the definition and components of frailty. Clinically, this may help identify groups of individuals in need of care and facilitate understanding among researchers.

Despite having no study design restrictions, we did not identify any qualitative or mixed method studies about frailty reversal interventions. None of the included studies reported engaging participants in decision-making or incorporating participant experiences into intervention delivery. A recent scoping review [ 94 ] echoes this concern, as older adults worry that they are not involved in health and well-being decisions. It is known that engaging older adults in decision-making improves health outcomes [ 95 ]. Therefore, we recommend qualitative and mixed methods studies aiming to integrate the older adults’ perspective regarding intervention development, evaluation, or implementation.

Acknowledging that frailty is complex in nature, RCTs with a large sample size could be beneficial to investigate the social, psychological, and cognitive aspects of frailty, which have received little attention to date.

Among the studies that did not report frailty reversal as an outcome, behavioural enhancement was one of the interventions implemented. The use of behavioral enhancement has been associated with the development of self-management skills and the maintenance of long-term changes [ 69 ]. It is therefore our recommendation that more studies consider a behavioural enhancement approach to facilitate adherence to interventions and maintain the benefits of interventions over the long-term. Lastly, given that frailty assessments and measurements are inconsistent, there is a need for more work to standardize them.

Further to considering the perspectives of older adults with frailty, we recommend tailoring interventions to fit the needs and capabilities of individuals rather than generalizing it across an entire population. For example, Latham and colleagues [ 96 ] conducted a resistance training program with Vitamin D supplements over ten weeks for participants with certain functional limitations, such as dependence on others for activities of daily living, prolonged bed rest, or impaired mobility. Contrary to other studies reporting positive effects of resistance exercise, such as improved functional outcomes and decreased frailty scores during this period [ 53 , 58 , 67 , 68 ], Latham and colleagues reported increased fatigue and musculoskeletal injury risks, which may be related to the participants’ functional limitations. We, therefore, recommend tailoring interventions to match participants’ needs and abilities rather than having set durations, frequencies, or intensities of interventions. Another reason is that some older adults may have functional limitations affecting their ability to adhere to prescribed interventions, including the potential adverse effects of polypharmacy on intervention effectiveness [ 92 ].

Research results influence guidelines and expectations for delivering care, services, and programs [ 97 ]. Frailty is becoming a potential public and global health concern, as indicated by the inclusion of studies from North America, Europe, Asia, Australia, etc. This reinforces the need to prevent or reverse this geriatric syndrome. Future studies should investigate frailty in all continents to increase our understanding on the global challenges of expectations, implementation, or care delivery for frail older adults. Such information can facilitate the transfer of healthcare professionals between continents by bridging the knowledge gap concerning frailty, its interventions, and potential strategies for reversing the condition.

Strengths and limitations

Our study has strengths and limitations. We established a reproducible, systematic approach, from the literature search to screening and data extraction. Furthermore, the search strategy was guided and peer-reviewed by academic librarians with extensive knowledge of scoping and systematic reviews. We quality appraised included articles permitting us to have a better sense of the quality of the evidence on this topic. Although not formally published or registered, an a priori protocol approved by the research team guided this study. In comparison to the protocol, a few changes have been made to this study, such as not obtaining expert consultation and revising the research questions.

In terms of limitations, included studies were heterogeneous in their study objectives, frailty definition, frailty domain targeted, and intervention characteristics. Some studies used self-administered questionnaires as outcome measures to assess frailty, potentially increasing the risk of bias and making replication difficult because there is no guarantee of having the same responses among different participants. In addition, two studies did not report the characteristics of the intervention [ 19 , 73 ], and one indicated that participants were frail but did not specify how frailty was determined [ 68 ]. Lastly, we acknowledge that using only a few databases may have limited the number of studies we were able to find.

Conclusions

We used a narrative and descriptive approach to synthesize the included studies. Despite the lack of a standard definition of frailty, we observed similar interventions across studies that reported an outcome of frailty reversal and those that did not. When frailty reversal was indicated, we explored the meaning of the concept. We noted that the physical domain received the most attention across all studies. In contrast, the social domain received the least attention in studies with frailty reversal outcomes.

This study confirms that frailty is a complex and worrying geriatric syndrome. As the world’s population ages, frailty is becoming a serious issue for public and global health. Thus, it is crucial for frailty to be considered a holistic phenomenon with a multi-factor approach rather than merely a physical condition. This requires more research addressing multiple domains to target its prevention and reversal. Our findings indicate that reversing frailty requires that a person first be considered frail, regardless of how frailty is assessed. Although we discovered different ways of assessing frailty among the studies, a key highlight is the fact that the ability to reverse frailty may depend on how frailty is defined and measured. Hence, a consensus on what reverse frailty means is necessary. A promising but challenging area for future research could be qualitative analysis that explores frail older adults’ lived experiences and perspectives. This will guide the development and implementation of possible interventions to reverse this critical geriatric syndrome.

Data availability

Data supporting the findings of this study are available in the article [and its supplementary information files].

Abbreviations

Body Mass Index

Center for Epidemiologic Studies Depression Scale

Medical Literature Analysis and Retrieval System Online

Chronic obstructive pulmonary disease

Cardiopulmonary resuscitation

Frailty Index

Frailty Phenotype

Geriatric Depression Scale

High intensity

Instrumental Activities of Daily Living

Joanna Briggs Institute

Kihon checklist

Multi-component Exercise Program

Medical Subject Headings

Post-intervention follow-up

Peer Review of Electronic Search Strategies

Preferred Reporting Items for Systematic Reviews and Meta-Analyzes

Resident Assessment Instrument-Home Care

Randomized control trials

Resting metabolic rate

Resistance training

Short Physical Performance Battery

Template for Intervention Description and Replication

Standards for Reporting Implementation Studies

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Acknowledgements

We would like to thank the University of Ottawa Health Science Librarians: Valentina Ly (VL), Victoria Cole (VC), and Lindsey Sikora (LS), for their guidance in ensuring searching for relevant studies. Special thanks also go to Ojongetakah Enokenwa Baa and Mbi Ayuk Solange, who acted as secondary screeners for selecting relevant studies.

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Aurélie Tonjock Kolle, Krystina B. Lewis, Michelle Lalonde & Chantal Backman

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AK, the principal investigator, initiated the project, designed the search strategy, carried out data extracted, and performed an analysis of the findings. KL critiqued and guided the project’s direction, such as the research questions, methodology, and results. ML offered suggestions about the thesis design results, critiqued and provided feedback as needed. CB guided the development of the research topic, provided regular feedback, and edited and approved every stage of the project. All authors read and approved the final manuscripts.

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Kolle, A.T., Lewis, K.B., Lalonde, M. et al. Reversing frailty in older adults: a scoping review. BMC Geriatr 23 , 751 (2023). https://doi.org/10.1186/s12877-023-04309-y

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