an essay about sleep deprivation

Problem of Sleep Deprivation Cause and Effect Essay

Introduction.

• What is Sleep Deprivation?

Causes of Sleep Deprivation

• Effects of Sleep Deprivation

Managing Sleep Deprivation

Works cited.

The functioning of the human body is influenced by a number of factors, which are mainly determined by the health status of an individual. Oftentimes, people seek medication when the body deviates from its normal and usual functioning mechanisms. Through different activities and processes, the body is able to use energy and replenish itself. Sleeping is one of the activities that has a direct effect on the functioning of the body.

This sleep deprivation essay explores how the functioning of the human body is influenced by various factors, primarily determined by an individual’s health status. While most people do not understand the implications of sleep, human effectiveness solely depends on the amount of time dedicated to sleeping. However, for various reasons, people fail to get enough sleep daily, weekly, or on a regular basis.

What Is Sleep Deprivation?

This cause and effect of sleep deprivation essay defines sleep deprivation as a condition occurring among human beings when they fail to get enough sleep. Sleep deprivation is defined as a condition that occurs when human beings fail to get enough sleep. Many experts argue that sleep deficiency is widespread even though most people do not consider it to be a serious issue, which affects their (Gaine et al.). Sleep deprivation has become a major problem in the United States, with almost 47 million suffering from the condition (Wang and Xiaomin). This lack of sleep can lead to a variety of physical and mental health issues, impacting daily functioning and quality of life.

The present essay about sleep deprivation defines sleep deprivation as a condition that occurs among human beings when they fail to get enough sleep. Many experts argue that sleep deficiency is widespread even though most people do not consider it to be a serious issue that affects their lives. Sleep deprivation has become a major problem in the United States, with almost forty-seven million suffering from the condition (Wang and Xiaomin). Among other reasons, one may get insufficient sleep in a day as a result of various factors. Some people sleep at the wrong time due to busy daily schedules, while others have sleep disorders, which affect their sleeping patterns. The following segment of the paper discusses the causes of deprivation.

Sleep deprivation may occur as a result of factors that are not known to the patients. This is based on the fact that sleep deprivation may go beyond the number of hours one spends in bed. In some cases, the quality of sleep matters in determining the level of deprivation.

In this context, it is possible for one to be in bed for more than eight hours but suffer from the negative effects of sleep deprivation. Whilst this is the case, there are people who wake every morning feeling tired despite having spent a recommended number of hours in bed (Griggs et al.14367).

Sleep deprivation can be caused by medical conditions, which may include but are not limited to asthma, arthritis, muscle cramps, allergies, and muscular pain. These conditions have been classified by researchers as common medical conditions that largely contribute to most of the cases of sleep deprivation being witnessed in the United States.

Similarly, these medical conditions have a direct impact on not only the quality but also the time one takes in bed sleeping. It is worth noting that sometimes people are usually unconscious to realize that their sleep is not deep enough (Wang and Xiaomin). This also explains the reason why it is not easy for a person to recall any moment in life when he or she moved closer to waking up.

Treatment of cases like sleep apnea is important because it affects the quality of sleep without necessarily awakening the victim. This is because medical surveys have revealed fatal effects of sleep apnea, especially on the cardiovascular system. Besides these, one is likely to experience breathing difficulties caused by insufficient oxygen.

Even though the treatment of sleep deprivation is important, it has been found that some drugs used to treat patients may worsen the case or lead to poor quality of sleep. It is, therefore, necessary for the doctor to determine the best drugs to use. Discussions between doctors and victims are imperative in order to understand patients’ responses (Conroy et al. 185).

Sleep deprivation is also caused by sleep cycle disruptions, which interfere with the fourth stage of sleep. Oftentimes, these disruptions are described as night terrors, sleepwalking, and nightmares.

Though these disorders are known not to awaken a person completely, it is vital to note that they may disrupt the order of sleep cycles, forcing a person to move from the fourth stage to the first one. Victims of these disruptions require attention in order to take corrective measures.

In addition, there are known environmental factors which contribute to several cases of sleep deprivation. However, doctors argue that the impact on the environment is sometimes too minimal to be recognized by people who are affected by sleep deficiency (Gaine et al.). In other words, these factors affect the quality of sleep without necessarily arousing a person from sleep.

Common examples include extreme weather conditions, like high temperatures, noise, and poor quality of the mattress. As a result, they may contribute to a person’s awakening, depending on the intensity when one is sleeping.

Moreover, the impact of these factors may develop with time, thus affecting one’s quality of sleep. In addition, most of the environmental factors that contribute to sleep deprivation can be fixed easily without medical or professional skills. Nevertheless, the challenge is usually how to become aware of their existence.

Lastly, sleep deprivation is caused by stress and depression, which have been linked to other health disorders and complications. Together with some lifestyles in America, these factors are heavily contributing to sleep deficiency in most parts of the world. Even though they might not be acute enough to awaken an individual, their cumulative effects usually become significant.

There are countless stressors in the world that affect youths and adults. While young people could be concerned with passing exams, adults are normally preoccupied with pressure to attain certain goals in life. These conditions create a disturbed mind, which may affect a person’s ability to enjoy quality sleep.

Sleep deprivation has a host of negative effects which affect people of all ages. The commonest effect is stress. Most people who suffer from sleep deficiency are likely to experience depression frequently as compared to their counterparts who enjoy quality sleep (Conroy et al. 188). As a result, stress may lead to poor performance among students at school.

Research has revealed that students who spend very few hours in bed or experience disruptions during sleep are likely to register poor performance in their class assignments and final exams. Additionally, sleep deprivation causes inefficiency among employees.

For instance, drivers who experience this disorder are more likely to cause accidents as compared to those who are free from it (Griggs et al.14367). This is based on the fact that un-refreshed people have poor concentration and low mastery of their skills.

Besides stress and anxiety, sleep deprivation has a wide-range of health-related effects. For instance, medical experts argue that people who spend less than six hours in bed are likely to suffer from high blood pressure. Quality sleep gives the body an opportunity to rest by slowing down the rate at which it pumps blood to the rest of the body (Wang and Xiaomin).

Inadequate sleep implies that the heart has to work without its normal and recommended rest. Additionally, sleep deprivation is known to affect the immune system. People who experience this disorder end up with a weakened immune system, leaving the body prone to most illnesses. This reduced immune response accumulates and may become fatal with time.

Sleep paralysis is also a common effect of inadequate sleep. This is due to disruption of the sleep cycle. It primarily occurs when the body is aroused during the fourth stage of the sleep cycle. In this case, the body is left immobile as the mind regains consciousness. Due to this conflict, one may experience pain and hallucinations.

Based on the negative effects of sleep deprivation, there is a need to manage this disorder among Americans. Firstly, it is necessary for people to seek medical advice concerning certain factors which could be contributing to this condition, like stress and infections (Wang and Xiaomin).

Proper counseling is also vital in stabilizing a person’s mental capacity. Physical exercises are also known to relieve a person from stressful conditions, contributing to sleep deficiency. Lastly, it is essential to ensure that the environment is free from noise and has regulated weather conditions.

Sleep deprivation remains a major problem in America, affecting millions of people. As discussed above, sleep deprivation is caused by a host of factors, ranging from environmental to health-related issues. Moreover, sleep deficiency has countless effects, most of which may become fatal in cases where the disorder is chronic.

Conroy, Deirdre A., et al. “ The Effects of COVID-19 Stay-at-home Order on Sleep, Health, and Working Patterns: A Survey Study of US Health Care Workers. ” Journal of Clinical Sleep Medicine , vol. 17, no. 2, Feb. 2021, pp. 185–91.

Gaine, Marie E., et al. “ Altered Hippocampal Transcriptome Dynamics Following Sleep Deprivation. ” Molecular Brain, vol. 14, no. 1, Aug. 2021.

Griggs, Stephanie, et al. “ Socioeconomic Deprivation, Sleep Duration, and Mental Health During the First Year of the COVID-19 Pandemic. ” International Journal of Environmental Research and Public Health, vol. 19, no. 21, Nov. 2022, p. 14367.

Wang, Jun, and Xiaomin Ren. “ Association Between Sleep Duration and Sleep Disorder Data From the National Health and Nutrition Examination Survey and Stroke Among Adults in the United States .” Medical Science Monitor , vol. 28, June 2022.

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Why are we so sleep deprived, and why does it matter?

Vice chair, Department of Neurology, University of Florida

Disclosure statement

Michael S. Jaffee does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

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As we prepare to “spring forward” for daylight saving time, many of us dread the loss of the hour’s sleep we incur by moving our clocks forward. For millions, the loss will be an added insult to the inadequate sleep they experience on a daily basis.

Surveys show that 40 percent of American adults get less than the nightly minimum of seven hours of sleep recommended by the American Academy of Sleep Medicine and the National Sleep Foundation. The National Institutes for Health estimate that between 50 million and 70 million people do not get enough sleep. These recommendations for minimal sleep are based on a review of many scientific studies evaluating the role of sleep in our bodies and the effects of sleep deprivation on our ability of our body to function at our peak performance level.

I am a neurologist at the University of Florida who has studied the effects of both traumatic brain injury and sleep impairment on the brain. I have seen the effects of sleep impairment and the significant effects it can have.

According to the National Sleep Foundation, American adults currently average 6.9 hours of sleep per night compared with the 1940s, when most American adults were averaging 7.9 hours a night, or one hour more each night. In fact, in 1942, 84 percent of Americans got the recommended seven to nine hours; in 2013, that number had dropped to 59 percent . Participants in that same Gallup poll reported on average they felt they needed 7.3 hours of sleep each night but were not getting enough, causing an average nightly sleep debt of 24 minutes. Fitbit in January 2018 announced results of a study it conducted of 6 billion nights of its customers’ sleep and reported that men actually get even less than women, about 6.5 hours.

Why sleep matters

The problems caused by sleep shortage go beyond tiredness. In recent years, studies have shown that adults who were short sleepers, or those who got less than seven hours in 24 hours, were more likely to report 10 chronic health conditions , including heart disease, diabetes, obesity, asthma and depression, compared to those who got enough sleep, that is, seven or more hours in a 24-hour period.

There are more challenges for children, as they are thought to have an increased sleep need compared to adults. The American Academy of Sleep Medicine recommends that children 6 to 12 years of age should sleep nine to 12 hours a day and teens 13 to 18 should sleep eight to 10 hours daily on a regular basis to promote optimal health.

A Sleep Foundation poll of parents suggested that American children are getting one hour of sleep or more per night less than what their body and brain require.

Researchers have found that sleep deprivation of even a single hour can have a harmful effect on a child’s developing brain. Inadequate sleep can affect synaptic plasticity and memory encoding, and it can result in inattentiveness in the classroom.

Every one of our biological systems is affected by sleep. When we don’t sleep long enough or when we experience poor quality of sleep, there can be serious biological consequences.

When we are sleep deprived, our bodies become more aroused through an enhanced sympathetic nervous system , known as “fight or flight.” There is a greater propensity for increased blood pressure and possible risk of coronary heart disease. Our endocrine system releases more cortisol, a stress hormone. The body has less glucose tolerance and greater insulin resistance, which in the long term can cause an increased risk of Type 2 diabetes. Also, sleep deprivation causes a reduction in growth hormone and muscle maintenance.

We also rely on sleep to maintain our metabolism. Sleep deprivation can lead to decreased release of the hormone leptin and increased release of the hormone ghrelin, which can be associated with increased appetite and weight gain.

The human body also relies on sleep to help with our immune system. Sleep deprivation is associated with increased inflammation and decreased antibodies to influenza and decreased resistance to infection.

Inadequate sleep has been associated with a negative effect on mood as well as decreased attention and increased memory difficulty. In addition, someone who is sleep deprived may experience a decrease in pain tolerance and in reaction times. Occupational studies have associated sleep deprivation with decreased performance, increased car accidents, and more days missed from work.

The role of the brain

Researchers have known for a while that brain health is an important aspect of sleep. Notably, sleep is an important part of memory consolidation and learning.

Newer research has suggested another important aspect of sleep for our brain: There is a system for the elimination of possibly harmful proteins such as abnormal variants of amyloid. This waste removal process, using what is known as the glymphatic system , relies on sleep to effectively eliminate these proteins from the brain. These are the same proteins found to be elevated in patients with Alzheimer’s disease. Studies show that older adults with less sleep have greater accumulations of these proteins in their brains.

Our sleep-wake cycle is regulated by the circadian system , which helps signal the brain to sleep using the release of the natural hormone melatonin. It turns out that our body’s system for regulating melatonin and our sleep schedule is most powerfully controlled by light.

There are cells in the retina of our eye that communicate directly with the brain’s biological clock regulators located in the hypothalamus and this pathway is most affected by light. These neurons have been found to be most affected by light waves from the blue spectrum or blue light. This is the kind of light most prominent in electronic lights from computers and smartphones. This has become a modern challenge that can adversely affect our natural sleep-wake cycle.

Additional factors that can hamper sleep include pain conditions, medications for other conditions, and the increased demands and connectedness of modern society.

As we prepare for daylight saving time, we can be mindful that many athletes have been including planned sleep extensions (sleeping longer than usual) into their schedule to enhance performance and that many professional sports teams have hired sleep consultants to help assure their athletes have enough sleep. Perhaps we should have a similar game plan as we approach the second Sunday in March.

• Sleep disorders
• Sleep deprivation
• Sleep apnea
• Daylight saving time
• Teens and sleep

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Among teens, sleep deprivation an epidemic

Sleep deprivation increases the likelihood teens will suffer myriad negative consequences, including an inability to concentrate, poor grades, drowsy-driving incidents, anxiety, depression, thoughts of suicide and even suicide attempts.

October 8, 2015 - By Ruthann Richter

The most recent national poll shows that more than 87 percent of U.S. high school students get far less than the recommended eight to 10 hours of sleep each night. Christopher Silas Neal

Carolyn Walworth, 17, often reaches a breaking point around 11 p.m., when she collapses in tears. For 10 minutes or so, she just sits at her desk and cries, overwhelmed by unrelenting school demands. She is desperately tired and longs for sleep. But she knows she must move through it, because more assignments in physics, calculus or French await her. She finally crawls into bed around midnight or 12:30 a.m.

The next morning, she fights to stay awake in her first-period U.S. history class, which begins at 8:15. She is unable to focus on what’s being taught, and her mind drifts. “You feel tired and exhausted, but you think you just need to get through the day so you can go home and sleep,” said the Palo Alto, California, teen. But that night, she will have to try to catch up on what she missed in class. And the cycle begins again.

“It’s an insane system. … The whole essence of learning is lost,” she said.

Walworth is among a generation of teens growing up chronically sleep-deprived. According to a 2006 National Sleep Foundation poll, the organization’s most recent survey of teen sleep, more than 87 percent of high school students in the United States get far less than the recommended eight to 10 hours, and the amount of time they sleep is decreasing — a serious threat to their health, safety and academic success. Sleep deprivation increases the likelihood teens will suffer myriad negative consequences, including an inability to concentrate, poor grades, drowsy-driving incidents, anxiety, depression, thoughts of suicide and even suicide attempts. It’s a problem that knows no economic boundaries.

While studies show that both adults and teens in industrialized nations are becoming more sleep deprived, the problem is most acute among teens, said Nanci Yuan , MD, director of the Stanford Children’s Health Sleep Center . In a detailed 2014 report, the American Academy of Pediatrics called the problem of tired teens a public health epidemic.

“I think high school is the real danger spot in terms of sleep deprivation,” said William Dement , MD, PhD, founder of the Stanford Sleep Disorders Clinic , the first of its kind in the world. “It’s a huge problem. What it means is that nobody performs at the level they could perform,” whether it’s in school, on the roadways, on the sports field or in terms of physical and emotional health.

Social and cultural factors, as well as the advent of technology, all have collided with the biology of the adolescent to prevent teens from getting enough rest. Since the early 1990s, it’s been established that teens have a biologic tendency to go to sleep later — as much as two hours later — than their younger counterparts.

Yet when they enter their high school years, they find themselves at schools that typically start the day at a relatively early hour. So their time for sleep is compressed, and many are jolted out of bed before they are physically or mentally ready. In the process, they not only lose precious hours of rest, but their natural rhythm is disrupted, as they are being robbed of the dream-rich, rapid-eye-movement stage of sleep, some of the deepest, most productive sleep time, said pediatric sleep specialist Rafael Pelayo , MD, with the Stanford Sleep Disorders Clinic.

“When teens wake up earlier, it cuts off their dreams,” said Pelayo, a clinical professor of psychiatry and behavioral sciences. “We’re not giving them a chance to dream.”

Teens have a biologic tendency to go to sleep later, yet many high schools start the day at a relatively early hour, disrupting their natural rhythym. Monkey Business/Fotolia

Understanding teen sleep

On a sunny June afternoon, Dement maneuvered his golf cart, nicknamed the Sleep and Dreams Shuttle, through the Stanford University campus to Jerry House, a sprawling, Mediterranean-style dormitory where he and his colleagues conducted some of the early, seminal work on sleep, including teen sleep.

Beginning in 1975, the researchers recruited a few dozen local youngsters between the ages of 10 and 12 who were willing to participate in a unique sleep camp. During the day, the young volunteers would play volleyball in the backyard, which faces a now-barren Lake Lagunita, all the while sporting a nest of electrodes on their heads.

At night, they dozed in a dorm while researchers in a nearby room monitored their brain waves on 6-foot electroencephalogram machines, old-fashioned polygraphs that spit out wave patterns of their sleep.

One of Dement’s colleagues at the time was Mary Carskadon, PhD, then a graduate student at Stanford. They studied the youngsters over the course of several summers, observing their sleep habits as they entered puberty and beyond.

Dement and Carskadon had expected to find that as the participants grew older, they would need less sleep. But to their surprise, their sleep needs remained the same — roughly nine hours a night — through their teen years. “We thought, ‘Oh, wow, this is interesting,’” said Carskadon, now a professor of psychiatry and human behavior at Brown University and a nationally recognized expert on teen sleep.

Moreover, the researchers made a number of other key observations that would plant the seed for what is now accepted dogma in the sleep field. For one, they noticed that when older adolescents were restricted to just five hours of sleep a night, they would become progressively sleepier during the course of the week. The loss was cumulative, accounting for what is now commonly known as sleep debt.

“The concept of sleep debt had yet to be developed,” said Dement, the Lowell W. and Josephine Q. Berry Professor in the Department of Psychiatry and Behavioral Sciences. It’s since become the basis for his ongoing campaign against drowsy driving among adults and teens. “That’s why you have these terrible accidents on the road,” he said. “People carry a large sleep debt, which they don’t understand and cannot evaluate.”

The researchers also noticed that as the kids got older, they were naturally inclined to go to bed later. By the early 1990s, Carskadon established what has become a widely recognized phenomenon — that teens experience a so-called sleep-phase delay. Their circadian rhythm — their internal biological clock — shifts to a later time, making it more difficult for them to fall asleep before 11 p.m.

Teens are also biologically disposed to a later sleep time because of a shift in the system that governs the natural sleep-wake cycle. Among older teens, the push to fall asleep builds more slowly during the day, signaling them to be more alert in the evening.

“It’s as if the brain is giving them permission, or making it easier, to stay awake longer,” Carskadon said. “So you add that to the phase delay, and it’s hard to fight against it.”

Pressures not to sleep

After an evening with four or five hours of homework, Walworth turns to her cellphone for relief. She texts or talks to friends and surfs the Web. “It’s nice to stay up and talk to your friends or watch a funny YouTube video,” she said. “There are plenty of online distractions.”

While teens are biologically programmed to stay up late, many social and cultural forces further limit their time for sleep. For one, the pressure on teens to succeed is intense, and they must compete with a growing number of peers for college slots that have largely remained constant. In high-achieving communities like Palo Alto, that translates into students who are overwhelmed by additional homework for Advanced Placement classes, outside activities such as sports or social service projects, and in some cases, part-time jobs, as well as peer, parental and community pressures to excel.

William Dement

At the same time, today’s teens are maturing in an era of ubiquitous electronic media, and they are fervent participants. Some 92 percent of U.S. teens have smartphones, and 24 percent report being online “constantly,” according to a 2015 report by the Pew Research Center. Teens have access to multiple electronic devices they use simultaneously, often at night. Some 72 percent bring cellphones into their bedrooms and use them when they are trying to go to sleep, and 28 percent leave their phones on while sleeping, only to be awakened at night by texts, calls or emails, according to a 2011 National Sleep Foundation poll on electronic use. In addition, some 64 percent use electronic music devices, 60 percent use laptops and 23 percent play video games in the hour before they went to sleep, the poll found. More than half reported texting in the hour before they went to sleep, and these media fans were less likely to report getting a good night’s sleep and feeling refreshed in the morning. They were also more likely to drive when drowsy, the poll found.

The problem of sleep-phase delay is exacerbated when teens are exposed late at night to lit screens, which send a message via the retina to the portion of the brain that controls the body’s circadian clock. The message: It’s not nighttime yet.

Yuan, a clinical associate professor of pediatrics, said she routinely sees young patients in her clinic who fall asleep at night with cellphones in hand.

“With academic demands and extracurricular activities, the kids are going nonstop until they fall asleep exhausted at night. There is not an emphasis on the importance of sleep, as there is with nutrition and exercise,” she said. “They say they are tired, but they don’t realize they are actually sleep-deprived. And if you ask kids to remove an activity, they would rather not. They would rather give up sleep than an activity.”

The role of parents

Adolescents are also entering a period in which they are striving for autonomy and want to make their own decisions, including when to go to sleep. But studies suggest adolescents do better in terms of mood and fatigue levels if parents set the bedtime — and choose a time that is realistic for the child’s needs. According to a 2010 study published in the journal Sleep , children are more likely to be depressed and to entertain thoughts of suicide if a parent sets a late bedtime of midnight or beyond.

In families where parents set the time for sleep, the teens’ happier, better-rested state “may be a sign of an organized family life, not simply a matter of bedtime,” Carskadon said. “On the other hand, the growing child and growing teens still benefit from someone who will help set the structure for their lives. And they aren’t good at making good decisions.”

They say they are tired, but they don’t realize they are actually sleep-deprived. And if you ask kids to remove an activity, they would rather not. They would rather give up sleep than an activity.

According to the 2011 sleep poll, by the time U.S. students reach their senior year in high school, they are sleeping an average of 6.9 hours a night, down from an average of 8.4 hours in the sixth grade. The poll included teens from across the country from diverse ethnic backgrounds.

American teens aren’t the worst off when it comes to sleep, however; South Korean adolescents have that distinction, sleeping on average 4.9 hours a night, according to a 2012 study in Sleep by South Korean researchers. These Asian teens routinely begin school between 7 and 8:30 a.m., and most sign up for additional evening classes that may keep them up as late as midnight. South Korean adolescents also have relatively high suicide rates (10.7 per 100,000 a year), and the researchers speculate that chronic sleep deprivation is a contributor to this disturbing phenomenon.

By contrast, Australian teens are among those who do particularly well when it comes to sleep time, averaging about nine hours a night, possibly because schools there usually start later.

Regardless of where they live, most teens follow a pattern of sleeping less during the week and sleeping in on the weekends to compensate. But many accumulate such a backlog of sleep debt that they don’t sufficiently recover on the weekend and still wake up fatigued when Monday comes around.

Moreover, the shifting sleep patterns on the weekend — late nights with friends, followed by late mornings in bed — are out of sync with their weekday rhythm. Carskadon refers to this as “social jet lag.”

“Every day we teach our internal circadian timing system what time it is — is it day or night? — and if that message is substantially different every day, then the clock isn’t able to set things appropriately in motion,” she said. “In the last few years, we have learned there is a master clock in the brain, but there are other clocks in other organs, like liver or kidneys or lungs, so the master clock is the coxswain, trying to get everybody to work together to improve efficiency and health. So if the coxswain is changing the pace, all the crew become disorganized and don’t function well.”

This disrupted rhythm, as well as the shortage of sleep, can have far-reaching effects on adolescent health and well-being, she said.

“It certainly plays into learning and memory. It plays into appetite and metabolism and weight gain. It plays into mood and emotion, which are already heightened at that age. It also plays into risk behaviors — taking risks while driving, taking risks with substances, taking risks maybe with sexual activity. So the more we look outside, the more we’re learning about the core role that sleep plays,” Carskadon said.

Many studies show students who sleep less suffer academically, as chronic sleep loss impairs the ability to remember, concentrate, think abstractly and solve problems. In one of many studies on sleep and academic performance, Carskadon and her colleagues surveyed 3,000 high school students and found that those with higher grades reported sleeping more, going to bed earlier on school nights and sleeping in less on weekends than students who had lower grades.

Sleep is believed to reinforce learning and memory, with studies showing that people perform better on mental tasks when they are well-rested. “We hypothesize that when teens sleep, the brain is going through processes of consolidation — learning of experiences or making memories,” Yuan said. “It’s like your brain is filtering itself — consolidating the important things and filtering out those unimportant things.” When the brain is deprived of that opportunity, cognitive function suffers, along with the capacity to learn.

“It impacts academic performance. It’s harder to take tests and answer questions if you are sleep-deprived,” she said.

That’s why cramming, at the expense of sleep, is counter­productive, said Pelayo, who advises students: Don’t lose sleep to study, or you’ll lose out in the end.

The panic attack

Chloe Mauvais, 16, hit her breaking point at the end of a very challenging sophomore year when she reached “the depths of frustration and anxiety.” After months of late nights spent studying to keep up with academic demands, she suffered a panic attack one evening at home.

“I sat in the living room in our house on the ground, crying and having horrible breathing problems,” said the senior at Menlo-Atherton High School. “It was so scary. I think it was from the accumulated stress, the fear over my grades, the lack of sleep and the crushing sense of responsibility. High school is a very hard place to be.”

We hypothesize that when teens sleep, the brain is going through processes of consolidation — learning of experiences or making memories. It’s like your brain is filtering itself.

Where she once had good sleep habits, she had drifted into an unhealthy pattern of staying up late, sometimes until 3 a.m., researching and writing papers for her AP European history class and prepping for tests.

“I have difficulty remembering events of that year, and I think it’s because I didn’t get enough sleep,” she said. “The lack of sleep rendered me emotionally useless. I couldn’t address the stress because I had no coherent thoughts. I couldn’t step back and have perspective. … You could probably talk to any teen and find they reach their breaking point. You’ve pushed yourself so much and not slept enough and you just lose it.”

The experience was a kind of wake-up call, as she recognized the need to return to a more balanced life and a better sleep pattern, she said. But for some teens, this toxic mix of sleep deprivation, stress and anxiety, together with other external pressures, can tip their thinking toward dire solutions.

Research has shown that sleep problems among adolescents are a major risk factor for suicidal thoughts and death by suicide, which ranks as the third-leading cause of fatalities among 15- to 24-year-olds. And this link between sleep and suicidal thoughts remains strong, independent of whether the teen is depressed or has drug and alcohol issues, according to some studies.

“Sleep, especially deep sleep, is like a balm for the brain,” said Shashank Joshi, MD, associate professor of psychiatry and behavioral sciences at Stanford. “The better your sleep, the more clearly you can think while awake, and it may enable you to seek help when a problem arises. You have your faculties with you. You may think, ‘I have 16 things to do, but I know where to start.’ Sleep deprivation can make it hard to remember what you need to do for your busy teen life. It takes away the support, the infrastructure.”

Sleep is believed to help regulate emotions, and its deprivation is an underlying component of many mood disorders, such as anxiety, depression and bipolar disorder. For students who are prone to these disorders, better sleep can help serve as a buffer and help prevent a downhill slide, Joshi said.

Rebecca Bernert, PhD, who directs the Suicide Prevention Research Lab at Stanford, said sleep may affect the way in which teens process emotions. Her work with civilians and military veterans indicates that lack of sleep can make people more receptive to negative emotional information, which they might shrug off if they were fully rested, she said.

“Based on prior research, we have theorized that sleep disturbances may result in difficulty regulating emotional information, and this may lower the threshold for suicidal behaviors among at-risk individuals,” said Bernert, an instructor of psychiatry and behavioral sciences. Now she’s studying whether a brief nondrug treatment for insomnia reduces depression and risk for suicide.

Sleep deprivation also has been shown to lower inhibitions among both adults and teens. In the teen brain, the frontal lobe, which helps restrain impulsivity, isn’t fully developed, so teens are naturally prone to impulsive behavior. “When you throw into the mix sleep deprivation, which can also be disinhibiting, mood problems and the normal impulsivity of adolescence, then you have a potentially dangerous situation,” Joshi said.

Some schools shift

Given the health risks associated with sleep problems, school districts around the country have been looking at one issue over which they have some control: when school starts in the morning. The trend was set by the town of Edina, Minnesota, a well-to-do suburb of Minneapolis, which conducted a landmark experiment in student sleep in the late 1990s. It shifted the high school’s start time from 7:20 a.m. to 8:30 a.m. and then asked University of Minnesota researchers to look at the impact of the change. The researchers found some surprising results: Students reported feeling less depressed and less sleepy during the day and more empowered to succeed. There was no comparable improvement in student well-being in surrounding school districts where start times remained the same.

With these findings in hand, the entire Minneapolis Public School District shifted start times for 57,000 students at all of its schools in 1997 and found similarly positive results. Attendance rates rose, and students reported getting an hour’s more sleep each school night — or a total of five more hours of sleep a week — countering skeptics who argued that the students would respond by just going to bed later.

For the health and well-being of the nation, we should all be taking better care of our sleep, and we certainly should be taking better care of the sleep of our youth.

Other studies have reinforced the link between later start times and positive health benefits. One 2010 study at an independent high school in Rhode Island found that after delaying the start time by just 30 minutes, students slept more and showed significant improvements in alertness and mood. And a 2014 study in two counties in Virginia found that teens were much less likely to be involved in car crashes in a county where start times were later, compared with a county with an earlier start time.

Bolstered by the evidence, the American Academy of Pediatrics in 2014 issued a strong policy statement encouraging middle and high school districts across the country to start school no earlier than 8:30 a.m. to help preserve the health of the nation’s youth. Some districts have heeded the call, though the decisions have been hugely contentious, as many consider school schedules sacrosanct and cite practical issues, such as bus schedules, as obstacles.

In Fairfax County, Virginia, it took a decade of debate before the school board voted in 2014 to push back the opening school bell for its 57,000 students. And in Palo Alto, where a recent cluster of suicides has caused much communitywide soul-searching, the district superintendent issued a decision in the spring, over the strenuous objections of some teachers, students and administrators, to eliminate “zero period” for academic classes — an optional period that begins at 7:20 a.m. and is generally offered for advanced studies.

Certainly, changing school start times is only part of the solution, experts say. More widespread education about sleep and more resources for students are needed. Parents and teachers need to trim back their expectations and minimize pressures that interfere with teen sleep. And there needs to be a cultural shift, including a move to discourage late-night use of electronic devices, to help youngsters gain much-needed rest.

“At some point, we are going to have to confront this as a society,” Carskadon said. “For the health and well-being of the nation, we should all be taking better care of our sleep, and we certainly should be taking better care of the sleep of our youth.”

About Stanford Medicine

Stanford Medicine is an integrated academic health system comprising the Stanford School of Medicine and adult and pediatric health care delivery systems. Together, they harness the full potential of biomedicine through collaborative research, education and clinical care for patients. For more information, please visit med.stanford.edu .

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Sleep Deprivation and Deficiency How Sleep Affects Your Health

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Getting enough quality sleep at the right times can help protect your mental health, physical health, quality of life, and safety.

How do I know if I’m not getting enough sleep?

Sleep deficiency can cause you to feel very tired during the day. You may not feel refreshed and alert when you wake up. Sleep deficiency also can interfere with work, school, driving, and social functioning.

How sleepy you feel during the day can help you figure out whether you're having symptoms of problem sleepiness.

You might be sleep deficient if you often feel like you could doze off while:

• Sitting and reading or watching TV
• Sitting still in a public place, such as a movie theater, meeting, or classroom
• Riding in a car for an hour without stopping
• Sitting and talking to someone
• Sitting quietly after lunch
• Sitting in traffic for a few minutes

Sleep deficiency can cause problems with learning, focusing, and reacting. You may have trouble making decisions, solving problems, remembering things, managing your emotions and behavior, and coping with change. You may take longer to finish tasks, have a slower reaction time, and make more mistakes.

Symptoms in children

The symptoms of sleep deficiency may differ between children and adults. Children who are sleep deficient might be overly active and have problems paying attention. They also might misbehave, and their school performance can suffer.

Sleep-deficient children may feel angry and impulsive, have mood swings, feel sad or depressed, or lack motivation.

Sleep and your health

The way you feel while you're awake depends in part on what happens while you're sleeping. During sleep, your body is working to support healthy brain function and support your physical health. In children and teens, sleep also helps support growth and development.

The damage from sleep deficiency can happen in an instant (such as a car crash), or it can harm you over time. For example, ongoing sleep deficiency can raise your risk of some chronic health problems. It also can affect how well you think, react, work, learn, and get along with others.

Mental health benefits

Sleep helps your brain work properly. While you're sleeping, your brain is getting ready for the next day. It's forming new pathways to help you learn and remember information.

Studies show that a good night's sleep improves learning and problem-solving skills. Sleep also helps you pay attention, make decisions, and be creative.

Studies also show that sleep deficiency changes activity in some parts of the brain. If you're sleep deficient, you may have trouble making decisions, solving problems, controlling your emotions and behavior, and coping with change. Sleep deficiency has also been linked to depression, suicide, and risk-taking behavior.

Children and teens who are sleep deficient may have problems getting along with others. They may feel angry and impulsive, have mood swings, feel sad or depressed, or lack motivation. They also may have problems paying attention, and they may get lower grades and feel stressed.

Physical health benefits

Sleep plays an important role in your physical health.

Good-quality sleep:

• Heals and repairs your heart and blood vessels.
• Helps support a healthy balance of the hormones that make you feel hungry (ghrelin) or full (leptin): When you don't get enough sleep, your level of ghrelin goes up and your level of leptin goes down. This makes you feel hungrier than when you're well-rested.
• Affects how your body reacts to insulin: Insulin is the hormone that controls your blood glucose (sugar) level. Sleep deficiency results in a higher-than-normal blood sugar level, which may raise your risk of diabetes.
• Supports healthy growth and development: Deep sleep triggers the body to release the hormone that promotes normal growth in children and teens. This hormone also boosts muscle mass and helps repair cells and tissues in children, teens, and adults. Sleep also plays a role in puberty and fertility.
• Affects your body’s ability to fight germs and sickness: Ongoing sleep deficiency can change the way your body’s natural defense against germs and sickness responds. For example, if you're sleep deficient, you may have trouble fighting common infections.
• Decreases   your risk of health problems, including heart disease, high blood pressure, obesity, and stroke.

Research for Your Health

NHLBI-funded research found that adults who regularly get 7-8 hours of sleep a night have a lower risk of obesity and high blood pressure. Other NHLBI-funded research found that untreated sleep disorders rase the risk for heart problems and problems during pregnancy, including high blood pressure and diabetes.

Daytime performance and safety

Getting enough quality sleep at the right times helps you function well throughout the day. People who are sleep deficient are less productive at work and school. They take longer to finish tasks, have a slower reaction time, and make more mistakes.

After several nights of losing sleep — even a loss of just 1 to 2 hours per night — your ability to function suffers as if you haven't slept at all for a day or two.

Lack of sleep also may lead to microsleep. Microsleep refers to brief moments of sleep that happen when you're normally awake.

You can't control microsleep, and you might not be aware of it. For example, have you ever driven somewhere and then not remembered part of the trip? If so, you may have experienced microsleep.

Even if you're not driving, microsleep can affect how you function. If you're listening to a lecture, for example, you might miss some of the information or feel like you don't understand the point. You may have slept through part of the lecture and not realized it.

Some people aren't aware of the risks of sleep deficiency. In fact, they may not even realize that they're sleep deficient. Even with limited or poor-quality sleep, they may still think they can function well.

For example, sleepy drivers may feel able to drive. Yet studies show that sleep deficiency harms your driving ability as much or more than being drunk. It's estimated that driver sleepiness is a factor in about 100,000 car accidents each year, resulting in about 1,500 deaths.

Drivers aren't the only ones affected by sleep deficiency. It can affect people in all lines of work, including healthcare workers, pilots, students, lawyers, mechanics, and assembly line workers.

Lung Health Basics: Sleep

People with lung disease often have  trouble sleeping. Sleep is critical to overall health, so take the first step to sleeping better: learn these sleep terms, and find out about treatments that can help with sleep apnea.

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Not getting enough sleep may make you feel years older

Insufficient sleep seems to result in people feeling older than they are, with a higher "subjective age" previously being linked to depression

27 March 2024

Prioritising sleep could make you feel younger

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Sleep deprivation could make you feel several years older than you really are.

How old someone feels, or their subjective age, has been associated with various physical and mental health outcomes , particularly depression . “Age is more than just the perception,” says Leonie Balter at the Karolinska Institute in Sweden. “We know those who feel younger than their actual age live healthier and longer.”

Given sleep’s importance for our mental and physical health, Balter and John Axelsson , also at the Karolinska Institute, decided to investigate if it affects our subjective age.

Why relaxation is as important as sleep - and six ways to do it better

The pair enlisted 429 people – aged 18 to 70 years old – to take a survey on how old they felt and how much they had slept in the past 30 days.

They found that reporting insufficient sleep was linked to the participants feeling older than they were, with each day of poor sleep adding an average of 0.23 years to their subjective age. In contrast, those who reported getting sufficient sleep throughout the 30 days had a subjective age that was 5.81 years younger on average than their real age.

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In the second part of the study, the pair recruited 186 more people. Over two weeks, these participants were asked to aim for 9 hours of sleep across two consecutive nights, recorded via a sleep log and sleep-tracking wrist device. They were then told to restrict their sleep to just 4 hours for two consecutive nights.

After this period of sleep restriction, they reported feeling an average of 4.44 years older than they were, while under the 9-hour sleep condition, they felt 0.24 years younger. Compared with those who felt the least fatigued, those who were the most tired reported feeling around 10 years older.

The findings show that sleep is a key indicator of how old some people might feel, which has been linked to our health , says Balter. “If you protect your sleep, you can feel younger,” she says.

Journal reference:

Proceedings of the Royal Society B: Biological Sciences DOI: 10.1098/rspb.2024.0171

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Do you actually need 8 hours of sleep every night?

Sleep is crucial for overall health and quality of life. Getting enough of it keeps our bodies and brains running and allows us to function throughout the day. How much is enough?

You’ve probably heard the widely-held belief that people need to get eight hours of sleep a night. But is this one-size-fits-all rule really true? In reality, many people sleep less than eight hours a night, and some sleep more.

Most of us know that sleeping too little can negatively impact our health. According to a new study , getting less than seven hours of sleep a night is associated a 7% increased risk of developing high blood pressure. The research, presented at the American College of Cardiology’s Annual Scientific Session, showed that sleeping less than five hours a night is linked to an 11% higher risk.

But what's considered "enough sleep" for the average person? Do you actually need eight hours of shuteye every night? We spoke to experts about how much sleep people need, the effects of sleep deprivation , and tips to get a better night's sleep.

Is 8 hours of sleep enough?

The “eight-hour rule” is actually more of a medical myth, Shelby Harris, Psy.D., a clinical psychologist specializing in sleep medicine and the director of sleep health at  Sleepopolis , tells TODAY.com. “It’s not actually that everyone needs eight hours. It’s that most people need between seven and nine. ... That’s where it comes from,” she adds.

Healthy adults need to sleep at least seven hours a night on a regular basis for optimal health, according to the American Academy of Sleep Medicine . So for most people, eight hours is enough.

These recommendations come from large population studies looking at how much sleep people need, Dr. Molly Atwood, Ph.D., assistant professor of psychiatry and behavioral sciences at Johns Hopkins Medicine, tells TODAY.com.

A person’s sleep need is the number of hours they would sleep naturally — without external constraints or alarms — in order to wake up feeling rested and function the next day.

Among adults, the distribution of sleep needs will look like a bell-shaped curve, with the vast majority of people falling somewhere between seven to nine hours, says Atwood. However, there are people on either side of the median and total outliers.

“It really does depend on the person," says Atwood. Some people only need six and a half hours of sleep every night, Atwood adds, whereas others may need more than nine hours to feel rested and function the next day.

Some individuals can sleep four hours a night and function normally without facing any harmful effects — but these so-called "short-sleepers" have a rare genetic mutation and only make up a tiny subset of the population, TODAY.com previously reported.

For everyone else, regularly sleeping less than seven hours a night is associated with adverse health outcomes, according to the AASM.

The relationship between sleep duration and morbidity and mortality has been well-studied, says Atwood. "What we typically see is that when you go below six or seven hours of sleep, you start seeing a stronger association between sleep and health problems or death," says Atwood. The further you go below seven hours on a regular basis, the higher the risk.

Good sleep quality and a consistent sleep schedule — going to bed and waking up around the time every day — are also important, the experts note.

When we sleep, the body cycles through four different stages of sleep, which are broken down into REM (rapid eye movement) sleep and non-REM sleep, Dr. Andrew Varga, a neuroscientist and physician at the Mount Sinai Integrative Sleep Center, tells TODAY.com.

Most people go through three to five cycles a night, with the duration of REM sleep getting longer each subsequent cycle later in the night, says Varga. This is referred to as the body’s “sleep architecture.”

Disrupted or abnormal sleep architecture can worsen the quality of sleep and over time, lead to sleep deprivation, the experts note. Sleep disorders like insomnia or sleep apnea , stress, and underlying health conditions can all affect sleep quality, says Harris.

Health effects of sleep deprivation

We all have sleepless nights from time to time, and it’s usually possible to catch up after a few days of sleeping the usual amount you need, the experts note.

When you consistently sleep too little without catching up, it can lead to sleep deprivation — which has a number of consequences.

“Sleep is important for pretty much every system in your body,” says Atwood.

In the short-term, sleeping well below the amount you need can cause deficits in cognitive functioning. The following day, people may experience delays in reaction time, poorer working memory, and difficulty paying attention or completing tasks, the experts note.

In addition to feeling drowsy and tired, people may notice their mood is affected after a night of too little sleep. "It might be a bit harder to regulate your emotions and you might feel more irritable or down," says Atwood.

In the long-term, chronic sleep deprivation increases the risk of cardiovascular problems, including heart disease, heart attack and stroke, Atwood says.

Research has shown that people who habitually sleep less than six hours a night also have a higher incidence of high blood pressure, kidney disease and diabetes, according to the experts. Sleeping too little can impact the immune system and affect metabolic functioning.

"There's more and more data coming out that it can increase your risk of cognitive issues as you get older, such as dementia," Atwood adds.

Chronic sleep deprivation is also associated with an increased risk of mental health problems including depression, bipolar disorder, and anxiety, TODAY.com previously reported . "If you're sleep deprived after a trauma, this increases the risk of PTSD," says Atwood.

How much sleep do you need?

The amount of sleep a person needs changes throughout different stages of life, and sleep needs will vary slightly depending on the individual and their health, behavior, and environment.

According to the latest  AASM recommendations , the following age groups need this much sleep on a regular basis:

• Infants (4 to 12 months) need 12 to 16 hours, including naps
• Children (1 to 2 years) need 11 to 14 hours, including naps
• Children (3 to 5 years) need 10 to 13 hours, including naps
• Children (6 to 12 years) need 9 to 12 hours
• Teenagers (13 to 18 years) need 8 to 10 hours
• Adults need 7 or more hours

Besides sleeping the recommended amount, you know you are getting enough sleep if you wake up feeling rested and refreshed, and you're able to function throughout the day without feeling an overwhelming drive to sleep, says Varga.

It's normal to feel a bit groggy right after waking up, says Atwood. but if this fatigue persists and you find yourself wanting to doze off the entire day, you're probably sleep deprived, she adds.

If you're getting the recommended seven to nine hours of sleep a night and still feeling sleepy or tired, this could be a sign of poor sleep quality, according to  the U.S. Centers for Disease Control and Prevention . Other signs include waking up throughout the night, snoring, and nighttime breathing difficulties.

Getting enough sleep every night is not always easy, the experts acknowledge. Life often gets in the way. Work obligations, school, parenting, lifestyle choices, and poor sleep hygiene are all common reasons why people do not get enough sleep, says Harris.

One-third of adults in the United States report that they usually get less than the recommended amount of sleep, per the CDC .

Tips to get more sleep

If you feel like you are not getting enough sleep or want to take steps to improve your sleep hygiene , the experts recommend taking the following steps:

• Create a wind-down routine every night.
• Make your sleeping environment comfortable, quiet, and dark.
• Avoid screens for 30 minutes to one hour before bedtime.
• Go to bed and wake up around the same time every day.
• Exercise regularly .
• Limit caffeine intake.
• Cut down on alcohol.
• Avoid taking naps too close to bedtime.

If you're taking steps to improve sleep hygiene and still find yourself struggling to get enough sleep most nights, the experts recommend talking to a doctor or a sleep medicine expert.

Caroline Kee is a health reporter at TODAY based in New York City.

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Woman&Home

Sleep deprivation: the effects and the foods that could help

Posted: May 21, 2023 | Last updated: July 21, 2023

Sleep deprivation effects and the foods that'll help you sleep better

We all know that smoking is bad for your health. Not to mention drinking too much alcohol, and eating too much fatty food. But have you ever seen a national campaign warning people about the dangers of sleep deprivation? Us neither, but the uncomfortable truth is that lack of sleep can do major damage to your health. 

In general, people need between seven to nine hours of sleep per night. Any less, and you’re increasing your chances of suffering from conditions including high blood pressure and heart disease. Yet how many of us actually get that amount of sleep on a regular basis? 

Worryingly, many of us think of sleep like a bank overdraft. We can miss a couple of hours here and there on weeknights, say, and catch up by having a Sunday lie-in, right? Wrong! In fact, research suggests it can take up to four days for your body to recover from a single hour of lost sleep. So if anything, it's more like having an overdraft where you get charged £50 for going overdrawn by £10. 

But here’s the good news. With so many of us working from home right now, we have a fresh opportunity to reorganise our schedules, and ensure we build in time for a decent sleep, night after night. And just in case you need further motivation, in this article we look at five effects of sleep deprivation you may not know about, and also let you know about some key foods that might just help you sleep better too.

By T3 staff

YOU'LL GET SICK MORE OFTEN

When we get sick, we rely on our immune system to fight back against the infection and make us well again. Research shows, however, that lack of sleep damages its ability to do so. For example, in  one study , researchers took blood samples from 11 pairs of identical twins with different sleep patterns. They discovered that the twin who slept least had the most depressed immune system of the two. 

This occurs because sleep is when our bodies both produces and releases cytokines: a class of small proteins that play a vital part in the immune process. Without them, your body is less able to fight off infections such as a cold, flu or Covid-19, even if you’ve received a vaccine. So you’re more likely to catch something nasty, and when you do, it’ll take longer to recover. Scary stuff.

YOU'LL GAIN WEIGHT

Studies show that people who sleep less than seven hours a day tend to gain more weight and have a higher risk of becoming obese than those who get more time in bed. This is because the bodies of sleep-deprived people have lower levels of leptin, a chemical that makes you feel full once you’ve eaten, as well as higher levels of ghrelin, a hormone that stimulates hunger. 

This effect is surprisingly fast acting. For example,  one study  found that one week of sleeping about five hours a night led participants to gain an average of two pounds in weight. 

The good news is that it works both ways: increasing the amount you sleep can help you lose weight. In  another study , 472 obese adults took part in a six-month weight loss programme. The researchers found that people who slept between six and eight hours a night had a greater chance of achieving their weight-loss goal than those who slept less.

YOU’RE MORE LIKELY TO GET DIABETES

A large body of research suggests that people who usually sleep less than eight hours a night have an increased risk of developing Type 2 diabetes (see  this study  for example). That’s because ongoing sleep deprivation means your body secretes more stress hormones, such as cortisol, which helps you stay awake. Unfortunately, this makes it harder for the hormone insulin to do its job properly in regulating our body’s  blood sugar levels .

This creates a vicious circle with the effect we noted above, where poor sleep increases your appetite and leads you to eat more fatty and sugar foods. This too will mess with your insulin and blood sugar levels, leading to a double whammy when it comes to the risk of getting Type-2 diabetes.

YOU'RE MORE LIKE TO SUFFER DEPRESSION

Everyone gets crabby after a poor night’s sleep. But the long term effects of continuous sleep deprivation can be much more serious when it comes to your mental wellbeing, causing or heightening conditions such as depression and anxiety.

That’s because sleep isn’t just about renewing our physical body, it’s also about recharging our brains and sorting through all the complex emotions we experience on a daily basis. REM sleep in particular appears to be especially important to processing painful and difficult memories, gradually blunting their sting and preventing us from reliving them over and over again, at least to the same level of intensity. Lack of sleep, though, stops our brains from doing this so well. 

The consequences of this can be wide ranging. For instance,  one study  found that sleep deprived people experience more negative thoughts, while  another  suggested they feel less grateful for their romantic partners.

YOU'LL HAVE LESS SEX

Not wanting to have sex is one of the less talked-about consequences of poor sleep, but it’s very real. That’s because, as we mentioned earlier, a lack of sleep leads to the release of cortisol, which reduces the production of testosterone production. (Although many people assume testosterone is just a male thing, it’s actually important to both men and women.)

One study , looking at 171 college-age women, found that an extra hour of sleep per night led to a 14% increase in the likelihood the women had sex the following day. The good news is that you don’t need to have silly amounts of sleep to make a difference: those women who reported improved drives slept for an average of just seven hours 22 minutes per night.

FOODS THAT'LL HELP YOU SLEEP BETTER

Having trouble sleeping? Then maybe your diet is to blame. There are changes you can make to give your body a better chance of getting a good night's kip, night after night. These are the foods you should be eating (and the ones to avoid) to improve your sleep habits. 

Let's begin by looking at how your general food habits influence your ability to sleep, then we'll reveal six foods that could help you sleep better.

GETTING THE TIMING RIGHT

It’s not just about what you eat but when you eat it. The most important thing is to avoid eating less than three hours before bedtime, which will mean you’re still digesting your food when you’re sleeping. 

This uses up vital bloodflow and energy that should be being used to repair your mind and body in the night, thus reducing the overall quality of sleep you enjoy. It may also lead to indigestion, heartburn, acid reflux and unnecessary trips to the bathroom, all of which will disrupt your sleep. 

For these reasons you should particularly try to avoid large meals, fatty foods, spicy foods and alcohol in the three hours before you go to bed. Also steer clear of citrus fruits, which can increase the levels of acid in your stomach and keep you up at night with heartburn.

FOODS TO AVOID FOR BETTER SLEEP

If you have a habit of eating processed foods, and other foods that are high in calories, sugar and fat, you shouldn’t be surprised if you have problems sleeping. These types of foods, which are known as high glycaemic index (GI), are broken down quickly by your body, causing a rapid spike in blood sugar. That feels nice while it's happening, but it's invariably followed by a sudden crash later, which just makes you crave more food. 

As well as encouraging diabetes and obesity, this can mess with your body’s circadian rhythms, which makes it more difficult to get a good night’s sleep. This in turn, makes you feel you lack energy, which encourages you to eat more, which leads to a vicious circle of poor sleep and binge-eating.

High GI foods include sugar, sugary foods, sugary soft drinks, white bread, potatoes, white rice, processed meats, and snacks such as biscuits, cakes, crisps and sweets. It’s not necessary to avoid such foods altogether, but if you’re having problems sleeping then at the very least you need to eat these in moderation.

FOODS THAT WILL HELP YOU GET BETTER SLEEP

If you really want to get a handle on your blood sugar then you need to include a lot of low GI and medium GI foods to your regular diet. These are broken down more slowly by the body, and cause a gradual rise in blood sugar levels over time.

Examples of medium GI foods include orange juice, honey, basmati rice and wholemeal bread, while low GI foods include unprocessed fish and meat, eggs, soy products, beans, fruit, milk, pasta, grainy bread, oats, and lentils. However, if such foods are roasted or fried in lots of fat then they'll then become high GI, so alternative methods such as steaming and baking are better if possible.

Of course, a little bit of what you fancy does you good, as they say, so you don’t need to get obsessed and try to be an angel. As long as you aim to eat a balanced diet, which may include low, medium and high GI foods – and should include at least five portions of fruit and vegetables a day – you should be able to avoid the kind of blood sugar spikes that lead to poor sleep patterns.

Another thing that can damage your sleep is too much stimulation from caffeine. So if you’re having problems sleeping, try cutting down not just on coffee but other sources of caffeine including tea and chocolate. 

As long as you follow the advice given so far, food and drink-related issues should no longer be keeping you awake at night. If you still need a little help getting to sleep, though, the following foods are widely believed to help. 

We say 'believed' because actually there’s no conclusive scientific proof that any of them work... yet, anyway. That said, none of them have as yet been  disproved , and there are some studies that suggest they do, so there’s no harm in trying.

Fish is high in vitamin B6, which encourages the production of the sleep hormone melatonin. Fatty fish is also a good source of vitamin D and omega-3 fatty acids, which are important in the production of the ‘happiness hormone’ serotonin, which is known to aid sleep. So you’d expect eating fish to help you sleep, and there’s a fair bit of research suggesting this might be true. 

For instance,  one study  found an association between consistent fish consumption and high sleep quality among Chinese schoolchildren, not to mention higher IQs. And another study  found that people who ate salmon three times per week enjoyed better sleep, as well as improved daytime functioning.

Vegetarians and vegans don’t need to feel conflicted though: you can also get B6 from leafy green vegetables such as spinach and cabbage, and Vitamin D from mushrooms and a range of fortified products such as fortified soy milk and fortified cereal.

Another place to find vitamin B6 is bananas: just one contains 33 percent of your daily requirement. What’s more, bananas also contain magnesium, which has been linked to lower stress levels; potassium, which acts as a muscle-relaxant; and melatonin itself. 

For these reasons, bananas are widely believed to encourage better sleep.  One study  found that banana consumption could significantly increase the concentration of melatonin in people’s blood after 120 minutes.

Almonds aren’t just a good, low-fat source of protein that can help to stabilize blood sugar as part of a balanced diet. It also contains magnesium, tryptophan, an amino acid that plays a central role in the production of serotonin, and large amounts of melatonin.  One study  found that feeding rats 400mg of almond extract led to them sleeping longer and more deeply.

If you do crave a late-night snack, then, almonds are a far better choice than sugary or fatty alternatives. If you’re not a fan though, other nuts such as walnuts, pistachios and cashews have similar qualities, as do seeds such as flax seeds, pumpkin seeds, and sunflower seeds.

4. MILK, DAIRY AND SOY MILK

Warm milk has been believed for generations to help you sleep, and that’s not surprising. Not only does it contain tryptophan, but the calcium it also contains helps our bodies to harness said tryptophan to manufacture melatonin. It also contains melatonin itself. 

The same goes for other dairy products including cheese and yoghurt, as long as they’re consumed in moderation. And vegans don’t need to miss out, either: soy milk contains tryptophan, too, and  research  suggests it can also have a sleep-inducing effect. 

5. SOUR CHERRY JUICE

Generally, sweet foods have a destabilising effect on blood sugar and are unlikely to encourage sleep; and sweet cherries are no exception. Sour cherries, also known as tart cherries or dwarf cherries, are different. 

Varieties such as Richmond, Montmorency, and English Morello contain above-average concentrations of melatonin. And in some studies, such as  this one , both tart cherries and their juice (when unsweetened) have been found to encourage sleep. 

6. CHAMOMILE TEA

Tea is generally to be avoided late at night, as it contains caffeine which is a stimulant that can interfere with sleep. Chamomile tea, however, is a good alternative as it contains apigenin, a chemical compound that binds to specific receptors in your brain that decrease anxiety and initiate sleep. In  one study , chamomile extract was found to help sleep-disturbed rats fall asleep.

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A new podcast examines the perils of intense meditation

Andrea Muraskin

Imagine it's a crisp clear winter day, and you're skiing down a mountain, feeling exhilarated. All of a sudden, you lose control of your skis. You're hurtling down towards the base of the slope, and all you can feel is abject terror.

That's how one young man explained his emotional state during an intensive meditation retreat. It was one of several troubling accounts reporter Madison Marriage heard while reporting Untold: The Retreat , a new investigative podcast series from the Financial Times and Goat Rodeo.

The four-episode series focuses on retreats held by the Goenka network, teaching a popular meditation technique called Vipassana. Participants follow a strict schedule, waking before dawn and meditating silently for 10 days, 10 hours per day. They eat just two vegan meals each day.

In Oregon, psilocybin treatment is an experiment in real time

Meditation and mindfulness have many known health benefits, including helping to process trauma and manage anxiety , improve eating habits, and ease chronic pain. While many participants say Goenka retreats changed their lives for the better, The Retreat tells the stories of individuals whose mental health deteriorated during a 10 day retreat – or for some, after several 10-day retreats.

Some spent time in psychiatric units, and two participants whose families spoke to Marriage, took their own lives.

If you or someone you know may be considering suicide or is in crisis, call or text 988 to reach the Suicide & Crisis Lifeline .

Marriage interviewed nearly two dozen people who had attended Goenka retreats in different countries, including the U.K., the United States, France, India, and Australia. According to these former participants, retreat staff all over the world had a similar reaction when they were approached with mental health problems. "They're going to be telling you the same thing, which is keep meditating even if you're in severe emotional distress," she told NPR.

A global organization, the structure of the Goenka network is decentralized. The Financial Times reached out for comment to lead teachers at several Goenka centers, including the centers in Delaware and British Columbia where participants had died by suicide after exhibiting signs of psychological distress. But they declined to do an interview or answer specific questions on the record.

Author Interviews

In 'hidden valley road,' a family's journey helps shift the science of mental illness.

Bob Jeffs, director of one Goenka center near Merritt, British Columbia, told the producers of The Retreat in a written statement that his staff assess applicants before retreats and tries to dissuade people who are not ready: "Although the experience of hundreds of thousands of people who have successfully completed retreats since the early 1970's is overwhelmingly positive, these courses are not for everyone. We take the safety and well-being of every student in our care extremely seriously."

Untold: The Retreat is a podcast from The Financial Times and Goat Rodeo. The Financial Times hide caption

NPR contributor Andrea Muraskin spoke with Marriage about what her investigation uncovered about the mental health risks of meditation retreats.

This interview has been edited for length and clarity.

Andrea Muraskin: What is Vipassana meditation and how is it taught at Goenka retreats?

Madison Marriage: Vipassana meditation is a type of meditation, which is ancient, its roots go back thousands of years... These retreats teach Vipassana meditation through the teachings of S. N. Goenka. And he's a kind of guru at the heart of this network, who founded the first meditation retreats back in the 1970s, and they've really proliferated.

Goenka's technique is that you spend a few days focusing on just one area of your body, and then it expands. And you have to shift your focus to different parts of your body. You wake up at 4 a.m., you start meditating at 4:30 a.m. You have a break at specific times, your day ends at 8, 9 p.m. And then in theory, you go to bed.

Muraskin: What did you discover about the Goenka retreats and mental health?

Mariage: I don't think many people associate the word meditation with anything negative. It sounds relaxing and something that you might do to help soothe yourself. And that's exactly the reason why a lot of people go off and do these retreats. They're looking for something that's going to help them to feel a bit more relaxed, a bit more calm, having a better headspace, that kind of thing.

I've now interviewed dozens of people who've done these retreats and have had the complete adverse reaction. It's almost like kind of jumping off a cliff in terms of their mental health. Some of these people have done two retreats or three retreats or ten retreats and really loved them. But there is a specific retreat where something in their mind clicks or breaks or snaps. Those are the kind of words that they've used.

Psychosis is really common. So [are] hallucinations, physical pain, like electrical zaps going up and down their bodies. In the first episode, [one young woman] describes it as being like stuck in a torture chamber for her mind.

The big one is terror, abject terror. I had one person email me this week saying, 'Thank you for making this podcast because I thought I was alone.' And he said that he would rather saw his own arm off than go back to that mental headspace.

One man in Britain ...was escorted out of a Goenka center in handcuffs by the police because he had to be sectioned at the local hospital and he wouldn't go voluntarily. There are people leaving these centers and heading to psychiatric units.

Muraskin: What did you learn about what's happening in the brains of people who have these adverse experiences with meditation?

Mariage: So we've interviewed several experts about what meditation does to the brain and one of the foremost experts we spoke to said it's a bit like a stimulant. So having lots of coffee or too much of any stimulants can end up having the opposite effect where instead of doing something good for you, it starts doing something bad, and it can begin to feel a little bit addictive. But there are limits to what the scientific community knows about the human brain and how and why it works in certain ways.

Muraskin: One of your interviewees told you she felt as if she had become addicted to meditation. There's no official diagnosis for meditation addiction in psychology. But did you speak to others who had experiences similar to addiction?

Mariage: Yes. Lots of people said that their first retreat or first several retreats really helped them and really brought them to quite an exciting spiritual plane. It almost sounds kind of mystical and godlike – you're on cloud nine mentally, and they come out and they feel calmer. They know how to process their thoughts better. Their life feels easier as a result. So they go to another. And they have kind of similar feelings, maybe not quite as intense.

And then the feeling starts to fade. So they do another retreat. And then a lot of people said that they ended up struggling to sleep. So they would meditate more because they had initially felt that meditation would help them to sleep because it had made them feel calmer at first. But effectively, they end up meditating through the night, all day, every day for weeks or months on end.

And then, I think maybe this comes back to your earlier question about impact on the brain – I would argue it's perhaps not meditation per se that is harming people's brains. A lot of the people I spoke to ended up having severe sleep deprivation. And it is clinically proven to be extremely bad for your brain not to sleep.

Muraskin: We've heard from several of our readers over time that they benefit from mindfulness and meditation. If somebody reading this interview becomes concerned, and thinks, I like my meditation practice, but should I be worried now, what would you say to someone like that?

Mariage: So the consensus from the psychologists and psychiatrists and academics I spoke to is that amounts of meditation up to half an hour a day on the whole is usually completely fine.

[The problem is] the extremity of this particular practice. Ten hours a day of meditating without any physical movement. You're sitting on the floor cross-legged with your eyes closed, meditating for 10 hours a day. You're put on a vegan diet. So for a lot of people that's far fewer calories, often at half of what they're usually used to. And there's no dinner. There's an element of sleep deprivation. And your sensory world is being massively diminished. And it's that which I think is driving people to quite extreme outcomes.

Muraskin: Do you think the psychological problems that came up during retreats could be explained by underlying mental health issues that the meditators had before they began meditating?

Mariage: I think that's a really difficult question because how can anyone know whether they have a mental health problem? You're meant to fill out a form before you go to one of these retreats and state whether or not you've ever had any kind of mental health issue or history of drug abuse. And if you've never had a mental health problem, you will of course say no and no, and in you go.

And I've spoken to people who say that they were completely stable prior to doing one of these retreats, had never had a mental or physical problem in their lives, and had never tried drugs, and they have gone in and they have emerged completely broken.

I actually think it's irrelevant whether or not somebody had a mental health issue beforehand, because the evidence that I've seen is that the particular format of these retreats can push people past their limits.

Muraskin: Based on your interviews with participants, is it difficult to leave a Goenka retreat early?

Mariage: Yes, it is difficult to leave a retreat early. [If you express the desire to], you're effectively gaslighted into staying.

You're told, oh, you might just be on the cusp of a breakthrough. The founder of this network died a decade ago, but it's still his voice and his teachings that are imparted at all of the retreat centers ...warning people that doing [this] practice is like undergoing surgery of the mind, and to leave halfway through is like walking out of an operation before you've been stitched up by the surgeon.

There was one man who said that every time he closed his eyes he could see streams of bubbles everywhere. And he didn't want to leave because he kind of wanted to fix that. and he thought, I might be stuck seeing streams of bubbles forevermore if I leave before the end of this.

At a lot of these centers you also hand in your keys and phone at the beginning, and that's quite an overt cue that you're here for the full period. You can of course go and ask someone and insist that you want them back, but several sources told me that when they expressed a desire to leave, they were pressured not to.

Muraskin: What did your sources –the meditators that experienced harm or their families – think needs to change to make these retreats safer?

Mariage: So first and foremost, warn people before they go in that mental health problems or kind of psychological distress is possible. It's a bit like putting warnings on bottles of medication that, you know, a tiny percentage of people with this prescription might have an adverse effect.

Secondly, they would like to see mental health practitioners on site. So rather than telling everybody to keep meditating, they need to be able to figure out better when somebody needs a bit more support and what that support should be.

Thirdly, they need proper emergency protocols. So for the two women who lost their lives after attending retreats, the horse had already bolted by the time their parents were contacted. I think it needs to be a lot more proactive in terms of reaching out to emergency contacts.

Muraskin: I can imagine you've received some pushback on the podcast from people who've really benefited from Vipassana retreats. What's your response to people who say you've painted the Goenka network too negatively?

Mariage: We've had a couple of emails from people who say this is really one-sided, you're not looking at the positive experiences at all, this has changed my life for the better.

But the podcast isn't about the people for whom this works.... The purpose is to scrutinize harm that is being done to people and to question why isn't the organization itself doing more to prevent that harm.

Andrea Muraskin is a contributor to NPR's Shots blog and writes the weekly NPR Health newsletter. She lives in Boston.

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Pentagon needs to wake up on troops’ lack of sleep, watchdog says

Even with a full arsenal of energy drinks and coffee rations, the U.S. military is still losing the war against sleepiness.

Despite promises from military leaders to address a lack of sleep among service members , most troops still fail to get enough rest each night to fully function at their posts , researchers warned in a report released this week.

“Fatigue and sleep deprivation among active-duty service members continues to be more the rule than the exception,” investigators from the Government Accountability Office wrote in findings released to Congress on March 26. “Impairment from fatigue can be equivalent to the effects of alcohol intoxication and increases the risk of collisions and mishaps.”

Past studies by Defense Department officials have shown that active-duty personnel are twice as likely as their civilian counterparts to sleep less than seven hours per night, leading to increased risk of accident and error in daily tasks.

A lack of sleep is breaking the US military

From the very start, unspoken principles are ingrained in service members. one such principle is that "sleep is a crutch.".

The new study — mandated by lawmakers in response to concerns from those past findings — said little progress has been made on the problem in recent years, even as military officials have promised that the issue is being taken seriously.

As part of a survey of military officers conducted by GAO, researchers found that more than one in four respondents slept for six hours or less per night, and half of all respondents rated the quality of their sleep as poor or extremely poor.

Problems included long hours spent at work, deployments interrupting sleep patterns, and medical issues from their military service that affect troops’ ability to rest.

“DOD and the services have taken steps to address fatigue, such as conducting research and implementing strategies to limit sleep deprivation,” researchers wrote.

“However, we found challenges with DOD’s approach to overseeing and leading the department’s fatigue related efforts, fragmented fatigue-related research efforts, and information sharing across the department.”

The GAO report found promise in some individual military services’ projects and guidelines designed to help troops get more rest, but noted that those separate efforts are not being analyzed or shared among the other armed forces, leading to incomplete results.

In 2021, Defense Department researchers outlined several recommendations to tackle the issue, including adopting new duty schedules to ensure eight hours of sleep, providing resources to troops who want to cut back on caffeine use, and establishing training in “sleep leadership” to emphasize the importance of the topic to commanders.

However, “DOD officials told us they do not have plans to implement and monitor the recommendations from that study, and officials were not able to provide an updated status on each of the recommendations,” the GAO researchers wrote.

The watchdog recommended moving ahead with those overdue changes, and assigning leaders within the services and Pentagon to spearhead the efforts. GAO leaders said that defense officials generally agreed with the ideas but did not provide any timeline for when or if changes will be made.

The full report is available at the GAO website.

Leo covers Congress, Veterans Affairs and the White House for Military Times. He has covered Washington, D.C. since 2004, focusing on military personnel and veterans policies. His work has earned numerous honors, including a 2009 Polk award, a 2010 National Headliner Award, the IAVA Leadership in Journalism award and the VFW News Media award.

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Coddling Plus Devices? Unequivocal Disaster for Our Kids.

In “The Anxious Generation,” Jonathan Haidt says we’re failing children — and takes a firm stand against tech.

Credit... Alex Merto

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By Tracy Dennis-Tiwary

Tracy A. Dennis-Tiwary is a professor of psychology and neuroscience, director of the Emotion Regulation Lab at Hunter College.

• Published March 26, 2024 Updated March 27, 2024
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THE ANXIOUS GENERATION: How the Great Rewiring of Childhood Is Causing an Epidemic of Mental Illness , by Jonathan Haidt

Imagine that your 10-year-old daughter gets chosen to join the first human settlement on Mars. She’s ready to blast off but needs your permission.

You learn that the billionaire architect of the mission hasn’t considered the risks posed by the red planet’s toxic environment, including kids developing “deformities in their skeletons, hearts, eyes and brains.”

Would you let her go?

It’s with this “Black Mirror”-esque morality play that Jonathan Haidt sets the tone for everything that follows in his erudite, engaging, combative, crusading new book, “The Anxious Generation.” Mars is a stand-in for the noxious world of social media. If we’d say no to that perilous planet, we should of course say no to this other alien universe.

Instead, we hem and haw about the risks, failing to keep our kids safely grounded in nondigital reality. The result can no longer be ignored: deformities of the brain and heart — anxiety, depression, suicidality — plaguing our youth.

Haidt, a social psychologist, is a man on a mission to correct this collective failure. His first step is to convince us that youth are experiencing a “tidal wave” of suffering. In a single chapter and with a dozen carefully curated graphs, he depicts increases in mental illness and distress beginning around 2012. Young adolescent girls are hit hardest, but boys are in pain, too, as are older teens.

The timing of this is key because it coincides with the rise of what he terms phone-based childhood. From the late 2000s to the early 2010s, smartphones, bristling with social media apps and fueled by high-speed internet, became ubiquitous. Their siren call, addictive by design and perpetually distracting, quickly spirited kids to worlds beyond our control.

It wasn’t phones alone. A second phenomenon coincided with the rise of the machines: the decline of play-based childhood. This change started in the 1980s, with kidnapping fears and stranger danger driving parents toward fear-based overparenting. This decimated children’s unsupervised, self-directed playtime and restricted their freedom of movement.

With parents and children alike stuck in “Defend mode,” kids were in turn blocked from discovery mode, where they face challenges, take risks and explore — the building blocks of anti-fragility, or the ability to grow stronger through adversity. Compared to a generation ago, our children are spending more time on their phones and less on, well, sex, drugs and rock n’ roll. While fewer hospital visits and teen pregnancies are obvious wins, less risk-taking overall could stunt independence.

That’s why parents, he argues, should become more like gardeners (to use Alison Gopnik’s formulation) who cultivate conditions for children to independently grow and flourish, and less like carpenters, who work obsessively to control, design and shape their offspring. We’ve overprotected our kids in the real world while underprotecting them in the virtual one, leaving them too much to their own devices, literally and figuratively.

It’s this one-two punch of smartphones plus overprotective parenting, Haidt posits, that led to the great rewiring of childhood and the associated harms driving mental illness: social deprivation, sleep deprivation, attention fragmentation and addiction. He has a lot to say about each of these.

Here is where his ideas and interpretation of research become contentious. Few would disagree that unhealthy use of social media contributes to psychological problems, or that parenting plays a role. But mental illness is complex: a multidetermined synergy between risk and resilience. Clinical scientists don’t look for magic-bullet explanations. They seek to understand how, for whom and in what contexts psychological problems and resilience emerge.

Haidt does recognize that nuance complicates the issue. Online — but not in the book — he and colleagues report that adolescent girls from “wealthy, individualistic and secular nations” who are “less tightly bound into strong communities” are accounting for much of the crisis. So perhaps smartphones alone haven’t destroyed an entire generation. And maybe context matters. But this rarely comes through in the book.

The final sections offer advice for reducing harmful, predatory aspects of technology and helping parents, educators and communities become more gardener and less carpenter. Some tips will be familiar (ban phones from school; give kids more independence). Other advice might give readers pause (no smartphones before high school; no social media before 16). Yet, taken together, it’s a reasonable list.

Still, Haidt is a digital absolutist, skeptical that healthy relationships between youth and social media are possible. On this point, he even rebuffs the U.S. Surgeon General’s more measured position. We’re better off banning phones in schools altogether, he asserts. Because, as he quotes a middle school principal, schools without phone bans are like a “zombie apocalypse” with “all these kids in the hallways not talking to each other.”

Whether or not you agree with the zombie apocalypse diagnosis, it’s worth considering the failure of prior absolutist stances. Nancy Reagan’s Just Say No drug campaign? A public health case study in what not to do. During the AIDS crisis, fear mongering and abstinence demands didn’t prevent unsafe sex. Remember the pandemic? Telling Americans to wear masks at all times undermined public health officials’ ability to convince them to wear masks when it really mattered.

Digital absolutism also risks blinding us to other causes — and solutions. In 1960s Britain, annual suicide rates plummeted. Many believed the drop was due to improved antidepressant medications or life just getting better. They weren’t looking in the right place. The phaseout of coal-based gas for household stoves blocked the most common method of suicide: gas poisoning. Means restriction, because it gives the despairing one less opportunity for self-harm, has since become a key strategy for suicide prevention.

“I’ve been struggling to figure out,” Haidt writes, “what is happening to us? How is technology changing us?” His answer: “The phone-based life produces spiritual degradation, not just in adolescents, but in all of us.” In other words: Choose human purity and sanctity over the repugnant forces of technology. This dialectic is compelling, but the moral matrix of the problem — and the scientific foundations — are more complex.

Yes, digital absolutism might convince policymakers to change laws and increase regulation. It might be a wake-up call for some parents. But it also might backfire, plunging us into defense mode and blocking our path of discovery toward healthy and empowered digital citizenship.

THE ANXIOUS GENERATION : How the Great Rewiring of Childhood Is Causing an Epidemic of Mental Illness | By Jonathan Haidt | Penguin Press | 385 pp. | $30

Inside the World of Gen Z

The generation of people born between 1997 and 2012 is changing fashion, culture, politics, the workplace and more..

For many Gen-Zers without much disposable income, Facebook isn’t a place to socialize online — it’s where they can get deals on items  they wouldn’t normally be able to afford.

Dating apps are struggling to live up to investors’ expectations . Blame the members of Generation Z, who are often not willing to shell out for paid subscriptions.

Young people tend to lean more liberal on issues pertaining to relationship norms. But when it comes to dating, the idea that men should pay in heterosexual courtships  still prevails among Gen Z-ers .

We asked Gen Z-ers to tell us about their living situations and the challenges of keeping a roof over their heads. Here’s what they said .

What is it like to be part of the group that has been called the most diverse generation in U.S. history? Here is what 900 Gen Z-ers had to say .

Young people coming of age around the world are finding community in all sorts of places. Our “Where We Are” series takes you to some of them .

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Neurocognitive Consequences of Sleep Deprivation

1 Division of Sleep and Chronobiology, Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania

Jeffrey S. Durmer

2 Fusion Sleep, Sleep Medicine Program, Suwanee, Georgia

David F. Dinges

Sleep deprivation is associated with considerable social, financial, and health-related costs, in large measure because it produces impaired cognitive performance due to increasing sleep propensity and instability of waking neurobehavioral functions. Cognitive functions particularly affected by sleep loss include psychomotor and cognitive speed, vigilant and executive attention, working memory, and higher cognitive abilities. Chronic sleep-restriction experiments—which model the kind of sleep loss experienced by many individuals with sleep fragmentation and premature sleep curtailment due to disorders and lifestyle—demonstrate that cognitive deficits accumulate to severe levels over time without full awareness by the affected individual. Functional neuroimaging has revealed that frequent and progressively longer cognitive lapses, which are a hallmark of sleep deprivation, involve distributed changes in brain regions including frontal and parietal control areas, secondary sensory processing areas, and thalamic areas. There are robust differences among individuals in the degree of their cognitive vulnerability to sleep loss that may involve differences in prefrontal and parietal cortices, and that may have a basis in genes regulating sleep homeostasis and circadian rhythms. Thus, cognitive deficits believed to be a function of the severity of clinical sleep disturbance may be a product of genetic alleles associated with differential cognitive vulnerability to sleep loss.

SLEEP DEPRIVATION AND ACCIDENT RISK

The overall prevalence of insufficient sleep in adults has been estimated at 20%. 1 The effects of insufficient sleep on cognitive processing are described below; of these, daytime sleepiness has been the most common measure assessed in population-based studies. One study determined the prevalence of daytime sleepiness using interviews conducted over 5.5 years which followed 1,007 randomly selected young adults ages 21 to 30 years in southeast Michigan. 2 That study found the average nocturnal sleep time during weekdays was 6.7 hours and on weekends was 7.4 hours. Sleepiness was inversely proportional to hours slept, and difficulty falling asleep was more prevalent in single adults with a full-time job. 2 Studies in young adults indicate that 8 to 9 hours of extended nocturnal sleep are needed to resolve sleepiness caused by decreased sleep time. 3 , 4 The apparent chronic partial sleep deprivation experienced by the young adults surveyed in 1997 complements statistics showing young drivers, especially males, are at much higher risk for drowsy driving and sleep-related crashes. 5 – 7

Sleep deprivation increases the risk of human-error-related accidents, 8 with such accidents estimated to have an annual economic impact of $43 to $56 billion. 9 Motor vehicle accidents related to fatigue, drowsy driving, and falling asleep at the wheel are particularly common, but often underestimated. 10 , 11 Increased time awake, nocturnal circadian phase, reduced sleep duration, prolonged driving duration, and use of soporific medications all contribute to the occurrence of drowsy-driving-related and fatigue-related motor vehicle crashes. 6 , 12 , 13 Moreover, studies of shift-workers, 14 – 16 truck drivers, 17 – 19 medical residents, 20 – 22 and airline pilots 23 – 26 all show an increased risk of crashes or near misses due to sleep deprivation in these populations.

Sleepiness-related motor vehicle crashes have fatality rates and injury severity levels similar to alcohol-related crashes. 6 In addition, sleep deprivation produces psychomotor impairments equivalent to those induced by alcohol consumption at or above the legal limit. 27 For example, in a study of simulated driving performance, impairments in lane-keeping ability after a night without sleep were equivalent to those observed at a blood alcohol content (BAC) of 0.07%. 28 Similarly, a study of professional truck drivers found that deficits in performance accuracy and reaction time after 28 hours of sleep deprivation were equivalent to those found after alcohol intoxication (BAC at 0.1%). 29 Thus, it appears that as continuous daytime waking exceeds 16 hours, psychomotor performance deficits increase to levels equivalent to BAC levels between 0.05% and 0.1%. 27 , 29

Sleep deprivation poses risks to safe operation in all modes of transportation and to performance in other safety-sensitive activities. 30 Improved understanding of the neural basis of such risks in operational environments has been achieved through the experimental study of how precisely sleep deprivation affects discrete cognitive abilities.

SLEEP DEPRIVATION AND SLEEP–WAKE REGULATION

The identification of the neural systems controlling circadian and sleep homeostatic mechanisms has improved our understanding of the effects of sleep deprivation on human neurobehavioral functions. 23 , 31 – 33 Although much is known about the neurobiology of hypothalamic mechanisms involving sleep–wake regulation, less is known about how these systems interact and alter waking neurocognitive functions. 34 , 35 Both wakefulness and sleep are modulated by an endogenous biological clock located in the suprachiasmatic nuclei (SCN) of the hypothalamus. Beyond driving the body to fall asleep and to wake up, the biological clock also modulates waking behavior, as reflected in sleepiness and cognitive performance, generating circadian rhythmicity in almost all neurobehavioral variables investigated. 34 , 35 Theoretical conceptualizations of the daily temporal modulation of sleep and wakefulness (and to a lesser extent the modulation of waking cognitive functions) have been instantiated in the two-process mathematical model of sleep regulation 36 , 37 and in mathematical variants of this model. 38 The two-process model of sleep regulation has been used to describe the temporal profiles of sleep and wakefulness. 34 , 35 The model consists of a sleep homeostatic process (S) and a circadian process (C), which interact to determine the timing of sleep onset and offset, as well as the stability of waking neurocognitive functions. 34 , 35 , 39 The homeostatic process represents the drive for sleep that increases during wakefulness and decreases during sleep. When this drive increases above a certain threshold, sleep is triggered; when it decreases below another threshold, wakefulness is invoked. The circadian process represents daily oscillatory modulation of these threshold levels. The circadian drive for wakefulness may be experienced as spontaneously-enhanced alertness in the early evening even after a sleepless night. Deprivation of sleep, however, can elevate homeostatic pressure to the point that waking cognitive functions will be degraded even at the time of the peak circadian drive for wakefulness. 40 The degradation of goal-directed cognitive behavior that can occur unpredictably in sleep-deprived individuals appears to reflect the transient intrusion of sleep neurobiology into waking neurobiology. 41

Sleep Propensity

Sleep deprivation increases sleep propensity, measured using polysomnography, as a reduction in the latency to sleep onset, 42 as well as by shortening of the latencies from lighter stages of non-rapid eye movement (NREM) sleep to deeper slow wave thalamocortical oscillations. 43 For example, after a night without sleep, the daytime sleep latency of a healthy adult decreases, by an order of magnitude, to less than a minute or two on average, and the subsequent latency from sleep onset to slow wave sleep is halved. 43 The Multiple Sleep Latency Test (MSLT) standardized sleep latency as a physiologic measure of sleepiness. 42 , 44 MSLT results may vary for many reasons, including prior sleep efficiency, prior sleep time, drug effects, physical activity, and posture. 45 , 46 The Maintenance of Wakefulness Test (MWT), a variant of the MSLT, also uses sleep latency to measure sleep propensity, but requires subjects to remain awake (resist sleep) rather than fall asleep. 47 Like the MSLT, the MWT shows reduced sleep latency in response to sleep deprivation. Thus, whether attempting to fall asleep or resist sleep, the latency from waking to sleeping is significantly reduced by sleep deprivation.

Microsleeps and Wake State Instability

The increased propensity for sleep to occur quickly, even when being resisted by a sleep-deprived subject, is consistent with evidence suggesting that “microsleeps” intrude into wakefulness when sleep-deprived subjects fail to respond (i.e., lapse) during cognitive performance demands. 48 – 51 Cognitive performance variability involving both errors of omission (i.e., behavioral lapses evident as failure to respond in a timely manner to a stimulus) and errors of commission (i.e., responses when no stimulus is present or to the wrong stimulus) is a primary consequence of sleep deprivation. 40 , 52 Such variability during performance in sleep-deprived subjects has been hypothesized to reflect wake state instability. 40 , 41 According to this theory, two competing neurobiologic systems exert an influence on the behavior of a sleep-deprived individual. More rostral areas of the brain exert a top-down drive to sustain alertness (i.e., motivated behavior), while more central and caudal areas increase the involuntary homeostatic drive to fall asleep. The interaction of these drives results in unreliable behavior, including heightened moment-to-moment variability in cognitive functions. A hallmark feature of cognitive variability is lapsing (i.e., brief periods of half a second to many seconds of no response). Lapses are often so brief, they cannot be detected in behavior without a special test, such as the Psychomotor Vigilance Test. 41 , 53 As lapses increase in frequency, they increase in duration, and ultimately they can result in a full-blown sleep attack (i.e., no spontaneous recovery by the subject). Both acute total sleep deprivation and chronic partial sleep deprivation can produce a high rate of lapsing that ultimately progresses to full and sustained sleep onset during goal-directed behavior (e.g., motor vehicle operation). 8 , 41

The difference between the lapse hypothesis and the state instability hypothesis is in the explanation for the variability in cognitive performance during sleep deprivation. The lapse hypothesis posits that cognitive performance during sleep deprivation is essentially “normal” until it becomes disrupted by lapses or brief periods of low arousal. 51 By contrast, the state instability hypothesis 40 posits that responses between lapses can also slow and get worse with time on task, that errors of commission (wrong responses) can comingle with errors of omission (lapses), and that variability in neurocognitive performance (more so than changes in average performance) increases as homeostatic sleep-initiating mechanisms become progressively more upregulated with sleep loss. 8 , 41 Thus, the brain’s capacity to maintain alertness is hindered by the activation of sleep processes.

Wake state instability occurs when sleep-initiating mechanisms repeatedly interfere with wakefulness, depending on the severity of sleep deprivation, making cognitive performance increasingly variable and dependent on compensatory mechanisms. 53 , 54 The ability of the sleep-deprived subject to engage in motivated behavior (e.g., walking) to compensate for or mask the cognitive effects of sleep loss is well recognized. 55 , 56 However, such a compensatory effort to resist sleep ultimately cannot prevent intrusions of sleep initiation into wakefulness. In addition to reports of sleep-deprived subjects “semi-dreaming” (likely hypnagogic reverie) while engaged in verbal cognitive tasks, 57 , 58 first-person reports exist of healthy sleep-deprived people falling asleep while ambulating in dangerous environments. 59 Thus, state instability evident in the cognitive performance and biobehavioral signs (e.g., slow eyelid closures 60 – 64 ) of sleep-deprived subjects, as reflected by the occurrence of microsleeps or sleep attacks, is directly related to increased variability in cognitive performance. The concomitant increase in errors of commission can also reflect an increased compensatory effort to resist sleep (i.e., trying to stop lapses by overresponding). Both cognitive errors of omission and of commission during sleep loss increase with time on task.

The effects of sleep deprivation on wake state instability during cognitive performance means that at any given moment in time the cognitive ability of the sleep-deprived individual is unpredictable, and a product of interactive, reciprocally inhibiting neurobiologic systems mediating sleep initiation and wake maintenance. Theoretically, wake state instability suggests there are multiple, parallel mechanisms by which waking and sleep states can interact. This theory is consistent with reports of the growing number of candidate molecules that may be involved in the co-occurrence of sleep and waking. 32

Cognitive Performance during Sleep Deprivation

It has long been established that sleep deprivation degrades aspects of cognitive performance. 52 , 57 , 65 The first published experimental study of the cognitive performance effects of sleep deprivation in humans was reported in 1896 and involved three adults experiencing 90 hours of continuous wakefulness. 56 Since 1896, many studies measuring behavioral changes associated with sleep deprivation have been performed. A review of the literature reveals three general types of studies: long-term total sleep deprivation studies (>45 hours), short-term total sleep deprivation studies (≤45 hours), and partial sleep deprivation studies (sleep restriction to <7 hours/24 hours). There are literally hundreds of published studies on the effects of total sleep deprivation, but far fewer on the effects of partial sleep deprivation, and only a handful on the effects of chronic partial sleep restriction. Moreover, the cognitive performance measures used vary widely among studies. Three categories of measurement commonly used in sleep deprivation studies include cognitive performance, motor performance, and mood. 66 Virtually all forms of sleep deprivation result in increased negative mood states, especially feelings of fatigue, loss of vigor, sleepiness, and confusion. Although feelings of irritability, anxiety, and depression are believed to result from inadequate sleep, experimental evidence of the existence of these mood states following sleep deprivation in a comfortable and predictable environment is thus far lacking. These alterations in mood, however, have been observed repeatedly when sleep deprivation occurs without regard for conditions. 67 On the other hand, self-reports of fatigue and sleepiness are often blunted in chronic sleep restriction relative to the more linear effects of chronic partial sleep loss on cognitive performance. 68

An early meta-analysis suggested that the effects of sleep deprivation on feelings of fatigue and related mood states are greater than the effects on cognitive performance and motor functions. 66 This conclusion, however, appears to be the result of inadequate experimental controls and cognitive assessments in partial sleep deprivation studies conducted prior to 1997. 69 Experiments in the past 10 years have found that chronic sleep restriction results in more rapid cumulative increases in cognitive performance errors than subjective measures of fatigue and mood, and the effects are in proportion to the dose of sleep and chronicity of restriction, 68 , 70 – 73 although rapid versus gradual restriction of sleep can influence the rate of accumulation of cognitive deficits. 68 , 74

Sleep deprivation induces a wide range of effects on cognitive functions ( Table 1 ), although cognitive tasks vary considerably in their sensitivity to sleep loss. In general, regardless of the task, cognitive performance becomes progressively worse when time on task is extended; this is the classic “fatigue” effect that is exacerbated by sleep loss. 48 , 75 However, performance on even very brief cognitive tasks that measure speed of cognitive “throughput,” working memory, and other aspects of attention have been found to be sensitive to sleep deprivation. 76 Two confounding factors that can obscure the effects of sleep loss on many cognitive tasks are intersubject variability and intrasubject variability. 53 For example, one individual’s poorest performance during sleep deprivation may be superior to that of the best performance of a non-sleep-deprived individual (this aptitude effect is the intersubject confound). Similarly, a person may be cognitively diminished by sleep loss, but continue to improve on a repeated task due to the effects of learning (this learning effect is the intrasubject confound). A second problem with many research reports on the cognitive effects of sleep deprivation concerns the nature of the dependent variables selected for analyses. A failure to understand that sleep deprivation increases variability within subjects (i.e., state instability) and between subjects (i.e., differential vulnerability to the effects of sleep deprivation) can mean that the effects of sleep loss on cognitive measures are missed because less sensitive metrics or data analyses are used. 77 , 78

Summary of Cognitive Performance Effects of Sleep Deprivation

To provide an accurate and useful measure of performance during sleep loss and the dynamic expression of waking neurobehavioral integrity as it changes over time, cognitive assessments must be valid and reliable reflections of fundamental waking functions altered by sleep deprivation. As such, measures of attention, vigilance, and declarative memory are often used, with reaction time as the dependent variable. The Psychomotor Vigilance Test (PVT), 79 a measure of behavioral alertness via sustained attention demands, is free of aptitude and learning effects and sensitive to sleep loss, 41 sleep pathology, and functioning at an adverse circadian phase. 53 , 80 The PVT requires continuous attention to detect randomly occurring stimuli. Such simple but attention-demanding tasks have proven to be reliable, valid, and sensitive measures of sleep deprivation, suggesting that the neural mechanisms of attention are among the most susceptible to sleep deprivation. The ubiquitous effects of sleep deprivation on attention-rich tasks should be understood relative to evidence that the dorsolateral prefrontal cortex is one of the critical structures in a network of anterior and posterior “attention control” areas. The prefrontal cortex has a unique executive attention role in actively maintaining access to stimulus representations and goals in interference-rich contexts. 81

More complex cognitive tasks involving higher cognitive functions have often been regarded as insensitive to sleep deprivation (see reference 65 for a review), perhaps due to the types of complex neurocognitive tasks utilized in some studies. In particular, the use of novel logic-based tasks results in little change following sleep loss. When tasks are made more divergent, such as occurs with multitasking and flexible thinking, sleep deprivation has been reported to produce adverse effects on performance. Divergent skills involved in decision making that are affected by sleep loss include assimilation of changing information, updating strategies based on new information, lateral thinking, innovation, risk assessment, maintaining interest in outcomes, mood-appropriate behavior, insight, and communication and temporal memory skills. 65 In one study utilizing divergent, complex skills, including visual temporal memory, confidence judgment, verb generation to noun presentation, and response inhibition, assessments were made in normal subjects from different age groups. 65 Performance on these cognitive skill areas was poorer in older subjects, but when young subjects were evaluated after 36 hours of sleep deprivation, their performance declined to those levels of the older subjects. The authors suggest that decrements in cognitive performance due to aging may be similar to the effects of sleep deprivation. Neurocognitive deficits in healthy aging have been attributed to deficits in the prefrontal cortex. 82 Both aging and sleep deprivation appear to reliably slow cognitive “throughput.”

Implicit to divergent thinking abilities is a heavy reliance on executive functions that require the prefrontal cortex. Executive function can be defined as “the ability to plan and coordinate a willful action in the face of alternatives, to monitor and update action as necessary and suppress distracting material by focusing attention on the task at hand.” 83 Many tasks believed to engage different aspects of executive function have been used in sleep deprivation studies. Examples include the Wisconsin Card-Sorting Task, the Tower of London Test, Torrance Tests of Creative Thinking, the Hayling sentence completion task, and Thurstone’s verbal learning task (see references 65 and 83 for reviews). Commonalities among these tasks include reliance upon working memory and attention systems. Working memory involves the ability to hold and manipulate information and can involve multiple sensory–motor modalities. Tests include presentation of visual, auditory, or tactile sensory information, utilized in verbal, mathematical, or spatial memory functions. Deficits in cognitive performance requiring working memory result in difficulty determining the scope of a problem due to changing or distracting information, 84 – 87 remembering the temporal order of information, 88 , 89 maintaining focus on relevant cues, 86 , 90 – 93 maintaining flexible thinking, 91 , 94 taking inappropriate risks, 95 , 96 having poor insight into performance deficits, 65 , 97 , 98 perseverating on thoughts and actions, 84 , 85 , 99 – 101 and having problems making behavioral modifications based on new information. 87 , 91 , 101

Although there is evidence that sleep deprivation adversely affects prefrontal cortex-related executive attention and working memory abilities, these cognitive effects are often not nearly as conspicuous or easy to measure as those involving basic processes such as cognitive and psychomotor speed, and lapses. Moreover, although executive functions clearly rely upon cortical activity, the role of subcortical systems (hypothalamus, thalamus, and brainstem) in purported prefrontal cortex-mediated deficits remains to be determined. Functional neuroimaging studies confirm that sleep loss affects prefrontal cortex activity, but there is also evidence (reviewed below) that the thalamus and possibly other midbrain and brainstem nuclei have important roles in the mechanisms underlying cognitive performance deficits in sleep-deprived subjects.

Functional Neuroimaging after Acute Total Sleep Deprivation

Functional neuroimaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have been increasingly used to examine the influence of sleep deprivation on brain metabolism and to relate changes in neural activity to behavioral performance decline and compensation (see references 102 – 105 for reviews). Among various domains of cognitive function, attention and working memory tasks predominate. These paradigms—mediated by reasonably well-understood brain networks involving the frontal and parietal cortices and subcortical structures including the thalamus and basal ganglia (see references 106 – 112 for reviews)—have been used to characterize the effects of sleep deprivation. Other tasks employed in neuroimaging studies on the effects of sleep deprivation include arithmetic calculation, 113 – 115 verbal learning, 116 – 118 logical reasoning, 119 spatial navigation, 120 inhibition control, 121 risky decision making, 122 and emotional processing. 123

PET STUDIES OF ACUTE TOTAL SLEEP DEPRIVATION

Wu and colleagues 124 conducted one of the earliest PET neuroimaging investigations exploring the effects of sleep deprivation on metabolism in the human brain. Their study used a continuous attention-demanding performance test and reported a significant reduction of absolute metabolic rates in the frontal and temporal lobes, thalamus, basal ganglia, and cerebellum without an overall decrease of whole brain metabolism following sleep deprivation. Greater reductions in absolute metabolic rates in the prefrontal cortex, thalamus, basal ganglia, and limbic regions after sleep deprivation were associated with greater deficits in vigilant attention as measured by reaction times. A more recent study from the same group, with an expanded number of subjects, replicated the findings that metabolism in the thalamus, basal ganglia, and frontal lobe decreases after 24 hours of sleep deprivation, and further reported that one night of recovery sleep only partially reversed metabolic reductions in these regions. 125 Using PET during the performance of serial addition/subtraction tasks that required both attention and arithmetic working memory, Thomas and colleagues 114 , 115 also found significant decreases in metabolic rates in the prefrontal cortex, anterior cingulate cortex, thalamus, and inferior parietal and temporal cortices across an 85-hour sleep deprivation period. The authors also reported that decreases in the thalamus, prefrontal cortex, and parietal cortices correlated with decreased cognitive performance and alertness over time.

Molecular tracers have also been used in PET studies to measure cerebral receptor changes following sleep deprivation. One study, using PET with F-18 CPFPX (8-cyclopentyl-3-(3-fluoropropyl)-1-propylxanthine) to quantify cerebral A1 adenosine receptor binding (A1AR) before and after sleep deprivation, found that deprivation increased A1AR binding in the human brain, particularly in the orbitofrontal cortex. 126 Another study used PET with C-11 raclopride and C-11 cocaine radiotracers to measure dopamine D 2 /D 3 receptors and transporters, respectively, and examined the effects of sleep deprivation on dopamine neurotransmission in the human brain. 127 Although sleep deprivation significantly decreased the specific binding of C-11 raclopride in the thalamus and striatum, which may reflect increases in dopamine cell firing and/or release after sleep deprivation, it did not change the binding of dopamine transporters in the striatum. A greater reduction in C-11 raclopride binding was associated with greater fatigue and sleepiness, and greater deficits in cognitive performance on visual attention and working memory tasks. The authors speculated that dopamine increases after sleep deprivation may underlie arousal maintenance in the presence of a greater homeostatic drive, but provide insufficient compensation for behavioral and cognitive impairment. 127

fMRI STUDIES OF ACUTE TOTAL SLEEP DEPRIVATION

In contrast to PET, which requires the injection of invasive and rapidly decaying radioactive tracers, fMRI using blood oxygenation level dependent (BOLD) contrast is noninvasive, more cost effective, and easier to use. In addition to measuring tonic neural activation by comparing task and control conditions with a block design, BOLD fMRI can detect phasic hemodynamic responses to brief stimuli at a rate of up to once every 2 seconds by utilizing an event-related experimental design. 128 With event-related BOLD fMRI, researchers can pseudo randomly intermix stimuli of different types and categorize events post hoc on the basis of the subject’s responses; this is necessary for studies to dissociate different performances during the same task conditions. Thus, BOLD fMRI has become the most widely used imaging method for localizing regional brain function and, as such, is more applicable to sleep deprivation studies than PET.

Attention tasks appear to be particularly sensitive to sleep loss. For example, Portas and colleagues 129 used fMRI with a block design and measured brain activity during similar performance of a short attention task under different levels of arousal, including a normal level of arousal, a higher level of arousal induced by caffeine administration, and a lower level of arousal induced by sleep deprivation. They found that arousal level modulated activation in the thalamus, with greater activation after sleep deprivation, but did not modulate activation in the prefrontal cortex, anterior cingulate cortex, and parietal regions. Another study used event-related fMRI and measured brain activity using the Psychomotor Vigilance Test after a normal night of sleep and after 36 hours of total sleep deprivation. 130 Faster reaction times were related to increased activation within a sustained attention cortical network and subcortical arousal and motor systems. By contrast, slower reaction times (which can include lapses), particularly after sleep deprivation, were associated with greater activation in the frontal and posterior midline regions, which may reflect a failure to disengage the “default-mode network.” 130

A series of fMRI experiments using various tasks involving attention and memory have investigated the effects of sleep deprivation on functioning. 113 , 131 – 145 Converging evidence from some fMRI studies have largely replicated the effects of sleep deprivation on decreased neural activity observed in PET studies. For example, using a serial subtraction task, Drummond and colleagues 113 found decreased activation in the prefrontal cortex, parietal lobe, and premotor cortex after sleep deprivation. Choo et al 136 found reduced activation in the parietal lobe and left thalamus after 24 and 35 hours of sleep deprivation during the performance of verbal working memory tasks. Similarly, other studies have also found decreased activation in the prefrontal cortex and parietal regions during the performance of a verbal working memory task. 137 , 138 A replication study with two pairs of rested wakefulness and sleep deprivation scans, showed that brain activation patterns were highly correlated across sessions and the magnitude of decreased activation in parietal regions was preserved and correlated with behavioral decline after sleep deprivation. 142 Tomasi and colleagues 144 used a visual ball-tracking task and found decreased activation in the frontoparietal regions, but increased activation in the thalamus.

In a recent experiment on the effects of sleep deprivation on lapses during performance on a visual selective-attention task, Chee and colleagues 141 also found reduced activation in the frontoparietal regions during lapses in addition to decreased mean activation in these regions after sleep deprivation ( Fig. 1 ). 141 Relative to lapses after a normal night’s sleep, lapses during sleep deprivation were associated with the expected reduction in activity in frontal and parietal control, but also a marked reduction in visual sensory cortex activation, as well as reduced thalamic activation. The latter contrasted with elevated thalamic activation during nonlapse periods. Despite these differences, the fastest responses after normal sleep and after sleep deprivation “elicited comparable frontoparietal activation, suggesting that performing a task while sleep deprived involves periods of apparently normal neural activation interleaved with periods of depressed cognitive control, visual perceptual functions, and arousal.” 141 These findings support the state instability hypothesis by providing evidence that neural changes are occurring rapidly and frequently in the brain when sleep-deprived subjects are attempting to maintain goal-directed behavior in the presence of elevated homeostatic sleep drive.

Functional magnetic resonance imaging (fMRI) responses from three cortical areas during a visual, global/local selective attention task performed by N = 24 healthy young adults when not sleep deprived (RW, in blue) and when sleep deprived (SD, in red) for one night. The graphs display differential neural responses in the medial frontal cortex (top), bilateral intraparietal sulcus (middle), and bilateral inferior occipital cortices (bottom), in association with the fastest 10% reaction times (RT) (left column) and the slowest 10% RTs (right column). A threshold of p < 0.001 was used to detect task-related activation. For both RW and SD states, slower responses were associated with higher peak fMRI signals in the medial frontal cortex and bilateral intraparietal sulcus (all p < 0.005). When comparing SD with RW, peak signal for the slowest 10% of trials was significantly lower in the parietal and occipital regions (right middle and bottom), but not in the medial frontal cortex (right top). SD also attenuated task-related thalamic activation (not shown). Peak signal in the occipital region after SD was significantly lower than RW even for the fastest 10% of trials (left bottom). However, there was no difference between RW and SD states in the frontal or parietal peak fMRI signals for the fastest responses across states (left top and middle). The shaded time points indicate those contrasted to assess significant state effects. The inset shows the mean peak signal associated with the time points under consideration. Error bars represent SEM. Significant differences between peak signals associated with a lapse and the average response for each state are marked with an asterisk. * p < 0.01, ** p < 0.001. (Reprinted from Chee et al, 141 with permission from The Journal of Neuroscience.)

Verbal Learning

Utilizing novel multivariate techniques as opposed to traditional group- and voxel-wise analyses, two independent studies 132 , 134 identified decreased activation as a function of sleep deprivation, which correlated with memory performance decline in nonverbal and verbal recognition tasks. By contrast, other fMRI studies have found increased regional neural activity in the frontoparietal network following sleep deprivation, suggesting that a neurobiologic compensatory mechanism for behavioral and cognitive impairment results from sleep loss. For example, Drummond et al 116 reported increased activation in the prefrontal cortex and parietal lobe during the performance of a verbal learning task after 35 hours of total sleep deprivation. Greater parietal activation was associated with better memory performance on this task. When arithmetic subtraction was combined with verbal learning in a divided attention task, 131 fMRI results replicated increased activation in the prefrontal cortex, anterior cingulate cortex, and parietal regions, and showed a positive association between parietal activation and memory performance after sleep deprivation. Chee and colleagues 133 reported increased activation in the prefrontal cortex during the performance of a more complex verbal working memory task, but not during the performance of a simple working memory task after sleep loss. Sleep deprivation also increased prefrontal cortex and temporal activation during the performance of a complex spatial navigation task. 120 Similarly, Mander and colleagues 143 found increased parietal activation during covert attention orientation following sleep deprivation. In addition, by manipulating the verbal learning task with two levels of word difficulty, increased activation was observed in the prefrontal cortex and parietal lobe in response to difficult, but not easy words after 36 hours of sleep deprivation. 117 Moreover, using a logic reasoning task with parametrically manipulated levels of task difficulty, 119 stronger linear neural responses were observed in the prefrontal cortex and parietal lobe associated with increasing task demands after sleep deprivation.

Taken together, the neuroimaging findings suggest the effect of sleep deprivation on brain regions subserving different cognitive functions may not be universal, but rather dependent on cognitive demands and on the difficulty level of the specific tasks used in a study. In addition, more complex or difficult tasks appear to permit recruitment of additional neural resources as part of compensatory neurocognitive mechanisms, which may make these tasks less vulnerable to sleep deprivation. By contrast, tasks that rely heavily on vigilant attention, even when simple and easy to do—such as PVT performance or driving—appear to involve no recruitable compensatory neurobiology to maintain performance in most (but perhaps not all) individuals.

Memory Acquisition and Retention

Sleep deprivation impairs visual short-term memory and limits its capacity. A recent fMRI study 140 used parametrically manipulated perceptual or memory load in two visual tasks, and found that both tasks showed declines in behavioral performance and reductions in parietal and extrastriatal activation after sleep loss. Critically, sleep deprivation reduced the linear relationship between memory load and parietal activation at rested wakefulness. Moreover, cholinergic augmentation with donepezil reduced the negative effects of sleep loss on behavioral performance across both tasks and increased parietooccipital activation in a manner that correlated with performance in individuals who were vulnerable to sleep deprivation. 146 Attention lapses following sleep loss compared with those after normal sleep were associated with reduced activation in the visual sensory cortex and thalamus. 141

Acute total sleep deprivation also produced a significant deficit in hippocampal activity during episodic memory encoding, resulting in worse subsequent retention. 118 Such findings suggest that a lack of sleep compromises the neural and behavioral capacity for committing new experiences to memory, which is essential for learning. Functional connectivity analysis showed that sleep deprivation increased connectivity between the hippocampus and basic alertness networks of the brainstem and thalamus on a memory consolidation task. 118 Like other neuroimaging studies, these findings support the notion that lower brain areas involved in arousal, sensory/perceptual gating, and attentional functions contribute to impairments in memory following sleep deprivation. This conclusion was recently confirmed by a transcranial magnetic stimulation study showing that stimulation in the left lateral occipital cortex improved memory function after sleep loss. 147

Emotional Memories and Emotional Processing

The role of sleep loss in consolidation of emotional (negative and positive) memories and in emotional processing has also been studied with fMRI. 123 , 145 In one study, sleep deprivation deteriorated recollection of both neutral and positive stimuli, but not negative stimuli. 145 Successful recollection of emotional stimuli elicited larger responses in the hippocampus and various cortical areas, including the medial prefrontal cortex, in the sleep group than in the sleep-deprived group. 145 When sleep deprived, recollection of negative items (but not positive items) elicited larger responses in the amygdala and an occipital area than when sleep was obtained. 145 Another study 123 used an emotional stimulus viewing task and demonstrated enhanced neural responses to negative stimuli in the amygdala and reduced functional connectivity between the amygdala and medial prefrontal cortex.

Expectations of Reward

The effects of a night of sleep deprivation on expectations of reward found that sleep loss elevated expectations of higher reward on a gambling task, as nucleus accumbens activation increased following risky choices, and it attenuated neural responses to gambling losses in the insular and orbito-frontal cortices. 122 However, sleep loss did not change behavioral performance on the gambling task, suggesting that neuroimaging may be more sensitive than behavior for detecting possible deficits in brain function following sleep deprivation.

INDIVIDUAL DIFFERENCES IN COGNITIVE VULNERABILITY TO ACUTE TOTAL SLEEP LOSS

Beyond task difficulty, interindividual differences may contribute to the inconsistent findings derived from functional neuroimaging studies. Behavioral studies have consistently reported large interindividual differences in cognitive responses to sleep deprivation, suggesting trait-like differential vulnerability 148 (see next section for further discussion). Most fMRI studies have used small samples (usually 10 to 30 subjects) and employed group-level analyses, both of which mask individual variation in a heterogeneous population. Several recent fMRI studies have examined brain activation patterns in subjects who appeared to be either cognitively more vulnerable versus less vulnerable to sleep loss. In one study, Mu and colleagues 138 compared brain activation between 10 more vulnerable and 10 less vulnerable young male subjects during performance of a working memory task at rested baseline (after normal sleep) and after sleep deprivation (when the vulnerability of subjects was defined based on their cognitive responses). Although both groups showed reduced frontoparietal activation after sleep deprivation, less vulnerable subjects showed significantly more activation both at rested wakefulness and after sleep deprivation. This finding is consistent with another working memory study that showed greater activation in left frontoparietal regions at rested wakefulness was associated with better memory performance after 24 hours of sleep deprivation. 139 The results from these two studies support the “cognitive reserve hypothesis,” which suggests that subjects who are less cognitively vulnerable to sleep loss may have more preexisting cognitive resources or a greater capacity to engage alternative neural resources as demand increases during sleep deprivation. 149

Unfortunately, results opposing this hypothesis have also been obtained. That is, better inhibition efficiency after sleep deprivation was associated with less activation in the right ventral prefrontal cortex at rested wakefulness using the go/no-go task. 121 Although several factors may account for the inconsistency of findings, it is noteworthy that all of these studies failed to prospectively phenotype subjects’ cognitive vulnerability to sleep deprivation before imaging them, which would have helped separate state and trait variance in these experiments. Given these inconsistent findings, additional studies are needed to understand the neural mechanisms mediating trait-like differential cognitive vulnerability to sleep deprivation in normal individuals that has been carefully documented. 148

Arterial Spin Labeled (ASL) Perfusion fMRI

Although findings from fMRI studies have significantly enriched our understanding of how sleep deprivation affects brain activation and how neural responses relate to cognitive and behavioral performance changes, several essential technical and methodological shortcomings of the BOLD contrast may limit its future application to sleep deprivation studies. BOLD contrast lacks absolute quantification and can only measure relative signal changes, which affects the accurate interpretation of observed sleep loss effects. Second, the presence of low frequency noise in the signal 150 , 151 decreases the sensitivity of BOLD fMRI for tracking slow neural activity changes for longer than a few minutes. 152 , 153 For this reason, BOLD imaging may be unsuitable for directly assaying sleep deprivation-induced neural activity changes occurring over a few days.

A recently developed neuroimaging technique—arterial spin labeled (ASL) perfusion fMRI—utilizes magnetically labeled arterial blood water as a diffusible tracer for blood flow measurements in a manner analogous to that used for 15O-PET scanning. 154 , 155 This technique provides a noninvasive imaging method to quantify cerebral blood flow (in mL/100 g per minute) during the performance of cognitive tasks 156 – 159 as well as during task-free resting states. 160 – 162 ASL-perfusion fMRI also offers reliable measures of cerebral blood flow with excellent reproducibility over long time periods. 153 , 163 These features suggest that ASL-perfusion fMRI may be a compelling method for functional imaging studies of sleep deprivation. Indeed, although no sleep deprivation study using ASL perfusion imaging has yet been published, preliminary data reported at scientific meetings 164 , 165 support the feasibility of this technique.

Cognitive Deficits from Chronic Partial Sleep Restriction

Although total sleep deprivation is a useful experimental paradigm for studying the neurocognitive effects of sleep deprivation, in reality it is a much less representative form of sleep loss than chronic partial sleep restriction. Chronic sleep restriction is common in modern society, due to a wide range of factors, including medical conditions, sleep disorders, work demands, and social and domestic responsibilities. 70 , 71 Many early studies of chronic partial sleep restriction reported conflicting effects on cognitive performance (see references 70 and 71 for reviews). Recent studies—using neurocognitive tasks sensitive to sleep deprivation and controlling those factors that in prior studies obscured accurate measurement of sleep restriction effects—found that 4 or more days of partial sleep restriction involving less than 7 hours sleep per night resulted in cumulative adverse effects on neurobehavioral functions. 68 , 72 , 73 Repeated days of sleep restriction to between 3 and 6 hours time in bed increased daytime sleep propensity, 73 , 166 decreased cognitive speed/accuracy as reflected in working memory tasks, 68 , 74 and increased lapses of attention on the Psychomotor Vigilance Test. 68 , 72 , 73

In the most extensive, controlled dose–response experiment on chronic sleep restriction to date, the neurocognitive effects of 14 days of sleep limitation to no more than 4, 6, or 8 hours in bed were compared with the effects of total sleep deprivation after 1, 2, and 3 nights without sleep. 68 Cognitive tasks, which were performed every 2 hours from 7:30 am to 11:30 pm each day, included the Psychomotor Vigilance Test, a working memory task, and cognitive “throughput” tasks. Subjective sleepiness was assessed and electroencephalogram (EEG) recordings were continuously obtained for power spectral analyses. Three days of total sleep deprivation resulted in significantly larger deficits than any of the three chronic sleep restriction conditions. No cognitive deficits occurred following 8 hours time in bed for sleep each night. After 2 weeks of sleep restriction to 4 hours time in bed per night, deficits in attention, working memory, and cognitive “throughput” were equivalent to those seen after two nights of total sleep deprivation. Similarly, 2 weeks of restriction to 6 hours time in bed per night resulted in cognitive deficits equivalent to those found after one night of total sleep deprivation. The cumulative cognitive deficits increased in a nearly linear manner over days of 4 and 6 hours time in bed. Subjective sleepiness and fatigue ratings showed much smaller increases, suggesting an escalating dissociation between subjective perceptions of sleepiness and actual cognitive performance capability. Slow wave activity (delta power) in the sleep EEG also showed little response to chronic sleep restriction, in marked contrast to slow wave activity after total sleep deprivation. This is a particularly provocative finding because it has long been assumed that slow wave sleep/EEG activity are associated with restorative sleep functions. 68 , 70 Apparently, as long as at least 4 hours of sleep time is permitted each night, slow wave activity does not reflect the homeostatic need for sleep during wakefulness. Thus, other aspects of physiologic functions occurring in the second half of a typical 7-to-8-hour sleep period appear essential for maintaining normal waking cognitive functions.

Surprisingly, the two aforementioned sleep restriction studies failed to find a linear relationship between the amount of sleep that subjects lost over days (i.e., sleep debt) and the magnitude of the cognitive performance deficits. Cognitive deficits accumulated much more rapidly when no sleep was allowed than when the same amount of sleep was lost more gradually over days of sleep restriction. 68 , 74 Drake and colleagues 74 interpreted this finding as evidence of adaptation to chronic sleep loss, although Van Dongen and colleagues 68 suggested that the crucial factor in producing daytime cognitive performance deficits was the cumulative amount of time subjects spent awake in excess of their usual wakefulness period ( Fig. 2 ). This finding suggests that there is a critical period of stable wake time within each circadian cycle after which neurocognitive deficits occur: this statistically estimated critical period was equal to 15.84 hours, and its associated sleep period was equal to 8.16 hours. 68 There are as yet no published studies to establish whether the same neural responses occur when cumulative cognitive deficits from chronic sleep restriction reach levels comparable to the deficits induced by acute total sleep deprivation.

A graphic comparison of performance on a behavioral alertness test following 14 days of partial sleep restriction or 3 days of total sleep deprivation, as a function of cumulative sleep debt (panel A) or cumulative excess wakefulness (panel B). Alertness was measured by lapses on the Psychomotor Vigilance Test (PVT). Cumulative sleep debt was determined by summating the difference between a statistically derived average sleep time of 8.16 hour/night and the actual hours of sleep each night (panel A). Cumulative excess wakefulness was determined by summating the difference between a statistically derived average daily wake time of 15.84 hour/day and the actual hours of wake each day (panel B). Each point represents the average time/day for each subject across 14 days of partial sleep restriction or 3 days of total sleep deprivation. Data from three partial sleep restriction groups (8 hours = diamond, 6 hours = square, and 4 hours = open circle) and one total sleep deprivation group (at days 1, 2, and 3 of total sleep deprivation = solid square) are shown. Panel A illustrates a difference (nonlinear relationship) between behavioral performance in the partial sleep restriction and total sleep deprivation groups as a function of cumulative sleep debt. Panel B demonstrates a similarity (linear relationship) between behavioral performance in the partial sleep restriction and total sleep deprivation groups as a function of cumulative excess wakefulness. The difference in analysis between panel A and panel B affects only the total sleep deprivation condition because subjects who receive 0 hours of sleep per day build up a statistically estimated average sleep debt of 8.16 hours per day, but extend their wakefulness by 24 hours per day. Thus, panel B shows a monotonic, near-proportional relationship between cumulative excess wakefulness and neurobehavioral performance deficits. (Reprinted with permission from Van Dongen et al. 68 )

Collectively, sleep restriction studies suggest that cumulative deficits in cognitive functions are more likely to occur and to accumulate to significant levels when sleep in healthy adults is reduced below 7 hours per night. 70 However, as in total sleep deprivation experiments, this conclusion must be tempered by the fact that there are substantial interindividual differences not only in basal sleep need, but also in resistance and vulnerability to the cognitive effects of sleep loss. 148 Moreover, the latter may have little relationship to the former. There is now compelling evidence that interindividual differences in cognitive deficits during sleep deprivation are systematic and trait-like, and the magnitude of these differences is substantial relative to the magnitude of the effect of prior sleep restriction. 148 Consequently, individual differences in neurocognitive responses to sleep deprivation are not merely a consequence of variations in sleep history. Rather, they involve trait-like differential vulnerability to impairment from sleep loss, for which neurobiologic or genetic correlates have yet to be uncovered.

Genetics of Sleep Deprivation

The stable, trait-like interindividual differences observed in response to total sleep deprivation 78 , 148 , 167 , 168 —with intraclass correlations ranging from 58 to 92% for neurobehavioral measures 78 , 148 —strongly suggest an underlying genetic component. Until recently, however, the genetic basis of such differential vulnerability to sleep loss in normal healthy subjects has received little attention 169 – 171 despite active ongoing genetics research in other related areas. For example, several studies have investigated frequency differences of sleep and circadian genetic polymorphisms in clinical (e.g., major depression and bipolar disorder 172 – 175 ) and nonclinical subjects. 176 , 177 Other studies have investigated specific genes involved in sleep and circadian rhythm sleep disorders, including insomnia, restless legs syndrome, narcolepsy, sleep apnea, and advanced and delayed sleep phase disorders (see references 178 – 180 for reviews).

By contrast, only a handful of studies have examined the role of human genetic polymorphisms on functioning in healthy subjects undergoing total sleep deprivation. One study found that the Val158Met polymorphism of catechol- O -methyltransferase (COMT) modulates the efficacy of modafinil on waking function, but neither this COMT genotype nor modafinil affected sleep-deprivation-induced changes in recovery sleep. 181 Another study from the same group reported an association between an A2A receptor gene polymorphism and objective and subjective differences in caffeine’s effects on NREM sleep after total sleep deprivation. 182

Three related studies investigated the role of the variable number tandem repeat (VNTR) polymorphism of the circadian gene PERIOD3 ( PER3 )—which shows similar allelic frequencies in African Americans and Caucasians/European Americans 183 , 184 and is characterized by a 54-nucleotide coding region motif repeating in 4 or 5 units—in response to total sleep deprivation by using a small group of the same subjects specifically recruited for the homozygotic versions of this polymorphism. Compared with the 4-repeat allele, the longer, 5-repeat allele ( PER3 5/5 ; n = 10) was associated with higher sleep propensity both at baseline and after total sleep deprivation, and worse cognitive performance, as assessed by a composite score of 12 tests, following total sleep deprivation. 185 A subsequent report—using the same 24 subjects—clarified that the PER3 5/5 overall performance deficits were selective: they only occurred on certain executive function tests, and only at 2 to 4 hours following the melatonin rhythm peak, from ~ 06:00 to 08:00. 186 Such performance differences are hypothesized to be mediated by sleep homeostasis. 185 , 186 Another publication on the same subjects showed that PER3 5/5 subjects had more slow wave sleep and elevated sympathetic predominance and a reduction of parasympathetic activity during baseline sleep. 187 These studies found no significant differences in the melatonin and cortisol circadian rhythms, PER3 mRNA levels, or in a self-report morningness–eveningness measure, 185 , 186 although another study using these same subjects found PER3 expression and sleep timing were more strongly correlated in PER3 5/5 subjects. 188 Other studies have shown that this polymorphism is associated with diurnal preference and delayed-sleep-phase syndrome. 189 – 192 Though compelling, these studies have yet to be replicated using independent, larger samples and thus should be considered preliminary. Indeed, we recently examined this genetic polymorphism and its relationship with cumulative neurobehavioral and homeostatic functions in chronic sleep restriction, 193 a condition more applicable to real world situations. We found that the PER3 VNTR polymorphism was not associated with individual differences in neurobehavioral responses to chronic sleep restiction, although it was slightly but significantly related to one marker of sleep homoeostatic response during chronic sleep restriction. The PER3 genotypes were comparable at baseline and showed equivalent inter-individual vulnerability to sleep restriction indicating that PER3 does not contribute to the neurobehavioral effects of chronic sleep loss. 193

Sleep Fragmentation: Experiments and Reality

Arousals during sleep are defined by polysomnography as abrupt increases in the EEG frequency for a minimum of 3 seconds during NREM sleep and in association with increases in the electromyographic frequency during REM sleep. 194 By definition, arousals do not result in awakenings; however, they have been associated with excessive daytime somnolence, 195 – 201 cognitive performance deficits, 195 , 198 , 202 – 206 and mood alterations. 198 , 203 , 206 , 207 These studies show that sleep fragmentation has the same effect as sleep deprivation on waking behavior. Experimental sleep fragmentation models that use aural stimulation to produce transient changes in heart rate and blood pressure, but not EEG (or cortical) arousal, have demonstrated significant increases in daytime somnolence using the MSLT and MWT. 208 In theory, one might expect waking neurocognitive deficits following the cumulative effect of multiple nights of sleep fragmentation. It has been suggested that arousals occurring at a rate of one per minute lead to daytime cognitive impairments associated with one night of sleep deprivation. 195 , 209 This scenario may be all too frequent, especially when specific populations with intrinsic sleep disorders are considered.

Obstructive sleep apnea (OSA) is a common disorder affecting between 2 and 4% of the adult population. 210 – 213 Episodic obstructive apneas are associated with hypoxemia and cortical arousals. OSA-related arousals are associated with increases in autonomic activity (heart rate and blood pressure) and may occur without cortical arousals. 208 , 214 – 216 Some investigators suggest that the severity of OSA due to hypoxemic neural damage may be related to deficits in executive function. 213 , 217 , 218 Reports indicate that neurophysiologic measures, such as the P300 latency of the event-related potentials in OSA patients show slowing and amplitude changes consistent with sleep-deprived subjects. 219 – 222 These changes persist months after apnea reversal with continuous positive airway pressure. 221 , 222 Sleep fragmentation has also been linked to deficits in sustained attention tasks as well as excessive daytime somnolence. 197 , 198 More recently, investigations of OSA in adults 223 and children 224 , 225 demonstrate that sleep apnea creates a pro-inflammatory state, which may precipitate other important chronic medical conditions, such as hypertension, type 2 diabetes, obesity, metabolic syndrome, stroke, and heart failure. A relationship may also exist between such inflammation and neurocognitive dysfunction in apneic patients. 226 , 227 At present, therapies targeting the inflammatory response in OSA have not been assessed with respect to their effects on cognitive function.

Neurocognitive deficits associated with OSA appear quite similar to those demonstrated in sleep deprivation and sleep fragmentation studies. A meta-analysis of cognitive dysfunction in sleep-disordered breathing patients using twenty-eight studies revealed several neurocognitive deficits associated with this spectrum of disease. 228 Moderate to large effect sizes were noted for performance on sustained attention tasks (i.e., Four Choice Reaction Time Test, Psychomotor Vigilance Test, and Continuous Performance Test), driving simulation, delayed visual memory retrieval, and working memory tasks requiring mental flexibility (i.e., Wisconsin Cart Sorting Task and Stroop Interference Trial). Verbal fluency tests showed small to moderate effect sizes, and short attention tasks (i.e., trail-making tests and cancellation tests), vigilance tests (i.e., Mack-worth Clock Performance and Parasumaran Vigilance Task), delayed verbal retrieval tasks and general intellectual function (i.e., full-scale intelligence quotient [IQ], Wechsler Adult Intelligence Scale-Revised [WAIS-R] estimated IQ, psychomotor efficiency factor, Processing Speed Index, and Mini-Mental Status Exam) all showed small effect sizes. No differences were found for reasoning tasks (i.e., WAIS-R Subtests Comprehension, Picture Arrangement, and Picture Completion), concept formation (i.e., WAIS-R Subtest Similarities and Wisconsin Cart Sorting Task) and immediate visual or verbal memory tasks. Notably, there was not enough data to identify a quantifiable change in overall executive functions in sleep-disordered breathing patients. Thus, a comprehensive array of deficits appears over a broad range of neurocognitive domains in OSA and sleep-related disordered breathing. This meta-analysis highlights several cognitive arenas that need further investigation in this population including working memory and executive function.

Restless legs syndrome (RLS) and periodic limb movement disorder (PLMD) represent two overlapping disorders that often lead to sleep fragmentation and excessive daytime sleepiness. Recent reports indicate that children with attention-deficit hyperactivity disorder (ADHD), with symptoms suggestive of ADHD, or with conduct problems have a higher incidence of RLS and PLMD. 229 – 234 Although attention deficits are easily demonstrable in these populations, it is unclear whether a cause-and-effect relationship between sleep fragmentation and cognitive deficits can be established. Recent studies comparing untreated RLS patients with control populations demonstrate statistically and clinically significant deficits in standard measures of executive function (similar to deficits reported after one night of total sleep deprivation in controls). 235 In additional experiments, prefrontal cortex function was assessed in RLS patients and compared with controls who underwent two weeks of partial sleep restriction. The results demonstrated that RLS patients perform significantly better than sleep-deprived controls on executive function tasks, suggesting a possible adaptation to sleep deprivation in RLS patients. 236 Taken together, these data suggest that sleep deprivation alone (as assessed in control subjects) may not account for the observed deficits in executive function noted in RLS. Indeed, other factors such as periodic limb movements, arousals, and/or dopaminergic dysfunction also may play a role. Additional neurocognitive assessments in RLS and PLMD are needed because these disorders offer a unique opportunity to study the effect of sleep fragmentation without hypoxemia on executive function. Any detectable cognitive deficits may be reversible with effective treatments such as dopaminergic therapy.

Sleep deprivation, whether a result of a clinical disorder or lifestyle choices, and whether acute or chronic, poses significant cognitive risks in the performance of many ordinary tasks such as driving and operating machinery. Theories of how sleep deprivation affects neurocognitive abilities are evolving rapidly as both the range of cognitive effects from sleep loss and the neurobiology of sleep–wake regulation are better understood. For example, recent experiments reveal that following chronic sleep restriction, significant daytime cognitive dysfunction accumulates to levels comparable to that found after severe acute total sleep deprivation. Executive performance functions subserved by the prefrontal cortex in concert with the anterior cingulate and posterior parietal systems seem particularly vulnerable to sleep loss. Following wakefulness in excess of 16 hours, deficits in attention and executive function tasks are demonstrable through well-validated testing protocols. Functional neuroimaging techniques indicate that wake state instability underlies many of the cognitive effects of sleep loss and involves sleep-promoting systems initiated during motivated behavior in which wake-promoting systems are active. Although neurophysiologic processes show similar changes across human brains following sleep deprivation, individual performance on cognitive measures vary greatly in response to sleep deprivation, suggesting trait-like (i.e., genetic) differential vulnerability or compensatory changes in the neurologic systems involved in cognition. New research has begun to investigate such possible genetic influences. Sleep-disordered breathing and nocturnal movement disorders show similar waking neurocognitive deficits to those seen in experimental sleep fragmentation protocols. Further studies of neurocognitive deficits in human disorders and following cumulative sleep restriction in healthy adults are needed. The results of such studies will have significant health implications for large segments of the population.

ACKNOWLEDGMENTS

This review was supported by grants NIH NR004281, AFOSR F49620-00-1-0266, and the National Space Biomedical Research Institute through NASA NCC 9–58 grant awarded to David F. Dinges. The review was also supported by a grant from the Institute for Translational Medicine and Therapeutics’ (ITMAT) Transdisciplinary Program in Translational Medicine and Therapeutics awarded to Namni Goel. The project described was supported in part by Grant Number UL1RR024134 from the National Center for Research Resources. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Center for Research Resources or the National Institutes of Health. Additional support was provided by Children’s Research Center grant 2–80225 and a Restless Legs Syndrome Foundation Research Grant awarded to Jeffrey S. Durmer and a Chinese NSF Grant awarded to Hengyi Rao.