Sleep Facts

The infographics on this page share some facts and stats that may surprise you.
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10 Interesting Facts about Sleep

Getting 7-9 hours of quality sleep every night is essential and necessary for a healthy and long life.

According to the CDC, 1/3 of US adults report getting less than the recommended amount of sleep. Continually not getting enough sleep can lead to many chronic diseases, like heart disease, obesity, and depression.2.1 Regularly getting 8 hours of sleep is essential to a healthy lifestyle. According to Dr. Markesha Brown, Director of the National Center on Sleep Disorders Research, “Healthy sleep encompasses three major things. One is how much sleep you get. Another is sleep quality—that you get uninterrupted and refreshing sleep. The last is a consistent sleep schedule.”2.2

Partial Sleep Deprivation or Partial Sleep Loss happens when someone consistently gets less than the 7 hours of recommended sleep per night. Missing any amount of sleep affects someone’s ability to keep their attention and be observant and aware, as well as having other impacts on your mind and body.2.3

Sleep is a necessary part of a healthy lifestyle, just as diet and exercise are. Lack of quality sleep can result in various physical and mental health problems. Getting enough sleep can improve your mood, reduce your risk of health problems, and make you more alert and ready for the day. The best way to start the day off on the right foot is to get 8 hours of quality sleep.

A Brief History of Sleep

The Stages of Sleep

Adenosine triphosphate (ATP), a nucleic acid, stores and provides energy to cells. Throughout the day, as your body uses energy, adenosine is produced as a byproduct. Adenosine is a neurotransmitter that promotes a person’s need for sleep otherwise known as your sleep drive.4.1 The more time we spend awake, the more our sleep drive grows. The pressure to sleep gets stronger as we go through our day and decreases and reaches a low after a full night of good-quality sleep.4.2

While you are asleep, you go through two phases of sleep – rapid eye movement (REM) and non-REM (NREM) sleep. Usually, four to six cycles occur per night, and the cycle restarts every 80 to 100 minutes. These stages of sleep are classified by brain activity and eye movement.

During these stages of sleep, your body uses less energy, allowing cells to resupply and prepare your body for the next day. While you are sleeping, your body has time to heal and repair injuries and issues that occured while awake. Sleep also allows for your brain to reorganize memories and information that was learned throughout the day, helping out with memory and recall.4.5

Why Are We Losing Sleep?

“Human beings are the only species that deliberately deprive themselves of sleep for no apparent gain. Many people walk through their lives in an underslept state, not realizing it.” – Matthew Walker, Director of the Center for Human Sleep Science at the University of California, Berkeley

The causes of sleep loss fall under a few main categories:

Another huge cause of sleep loss is social media. An American Academy of Sleep Medicine survey found that “93% of Gen Z have lost sleep because they stayed up ‘past their bedtime’ to view or participate in social media.”5.3 Another poll of hospital employees and university students found that 70% of people report using social media after getting into bed, and about 15% spend more than an hour each night doing so.5.4 

Not only does social media keep us awake, but laboratory studies have shown exposure to blue light that electronics emit before bed interferes with our brain’s production of melatonin, the hormone that helps regulate your sleep and wake schedule. About 21% of adults say that when they wake up in the middle of the night they check their phone, letting blue light interrupt their sleep, leading to a higher risk of losing sleep and developing sleep disorders.5.5 Even though scientists have found some convincing clues that blue light from screens and devices might alter our natural sleep patterns, it is not entirely certain how much of a problem it is in our daily lives. As light technology evolves, further research needs to be done to determine if low-level exposure to blue light over time can alter sleep patterns. However, there is enough evidence to suggest that one should be cautious about how much blue light we are exposed to before and during bedtime.

The Importance of Sleep for Our Body and Mind

“Do but consider what an excellent thing sleep is…that golden chain that ties health and our bodies together. Who complains of want? of wounds? of cares? of great men’s oppressions? of captivity? whilst he sleepeth?” – Thomas Dekker, The Gull’s Hornbook, 1609

Sleep and Our Body
Research shows that being chronically sleep-deprived (getting 7 hours or less of sleep more than two days in a row)6.1 disrupts hormone regulation, glucose metabolism, insulin resistance, inflammation processes, pain perception, and immune function. The effects of sleep loss on hormone regulation have led to research on how sleep affects obesity, diabetes, and cardiovascular disease.6.2 Many common medical issues and diseases impacting developed nations can be linked back to lack of sleep.6.3

Sleep and Our Mind

Poor sleep and lack of sleep can negatively affect the brain’s ability to express, regulate, and process emotions.6.12 It is also associated with difficulty in concentration and memory. Along with diet and exercise, sleep is a key pillar to a healthy lifestyle.

It is found that sleep helps to restore the brain by flushing out toxins that build up during waking hours. Cerebrospinal fluid (CSF) is a clear, watery fluid that surrounds and protects the brain and spinal cord. It moves through the brain and central nervous system through a series of channels. During wakefulness, CSF flow is slowed as brain cells are active and take up more space, however, CSF flow increases during non-REM stages of sleep by over 30 percent. This wave CSF washes out metabolic waste buildup from brain tissue that accumulates while we are awake during learning and active thinking, such as beta-amyloid, which is linked to Alzheimer’s disease.6.13

Sleep Debt

When you regularly sleep fewer hours than the recommended eight, you accumulate a sleep debt for the time lost. For example, if you lose one hour of sleep each night, you will have a sleep debt of seven hours after one week.7.1

Napping and sleeping-in are common approaches taken to make up for missed sleep and may help with daytime sleepiness and fatigue. However, one study found that catching up on sleep during the weekend is not effective in helping to prevent metabolic dysregulation that is associated with regularly not getting enough sleep, but it can help your body return to its normal sleep patterns.7.2

Research shows that it can take up to four days to recover from one hour of lost sleep and up to nine days to completely eliminate sleep debt.7.3 In one study, participants restricted their sleep by 30% every night for 10 days. After a full week of recovery and sleeping whenever they wanted, participants still had not returned to their optimal brain function.7.4 However, our body’s sleep and wake system is complex, and the effects of missed sleep cannot be entirely offset by getting extra sleep on subsequent nights. For example, you could sleep 7 hours for 2 nights in a row and then make it up with more than 8 hours of sleep the next night and have no hours of debt. However, getting 6 hours one night and 7 hours the next, since you are missing so many hours of sleep, you can’t make that up and have no hours of sleep debt left over. The best thing to do is practice healthy sleep habits to prevent the accumulation of sleep debt from the get-go.

Social Jetlag

“Our lives are governed by three clocks: the social clock that organizes our lives with others (local time), the biological clock that controls our physiology (circadian time) and the sun clock that defines natural light and darkness. The more misaligned these clocks are, the higher our odds of developing certain diseases.” – Till Roennenberg, German researcher who coined the term social jetlag in 2006

Social jetlag is a term used to describe the consequence of shifting between two schedules – one determined by work, school, and social obligations and the other by our internal clock. This phenomenon occurs when people have different sleep patterns on work/school days compared to days off, similar to the way jetlag happens when traveling across time zones.  According to Roennenberg, the term was inspired by a study that showed people who slept at different times during the work week and weekends had increased tobacco, caffeine, and alcohol consumption compared to those who kept regular sleeping hours during the week and weekend. It is estimated that around two-thirds of people experience at least one hour of social jetlag a week, and one-third experience two hours or more.8.2

Social jetlag can cause fatigue and make you feel tired due to the body’s internal clock not being in sync with local time. To help mitigate the impacts of social jetlag, it is important to maintain consistent sleep-wake schedules, especially on weekends or days off. By synchronizing your internal body clock to external demands such as work or socializing can help create healthy sleep patterns and reduce the impacts of social jetlag.

Naps

According to legend, while napping, Albert Einstein would “recline in his armchair with a spoon in his hand and a metal plate directly beneath. He’d allow himself to drift off for a second, then – bam! – the spoon would fall from his hand and the sound of it hitting the plate would wake him up.”8.1

A nap can be helpful for those who work odd hours or for people who did not get enough quality sleep the night before. Many have found that taking a brief afternoon nap can boost alertness and combat the mid-afternoon energy dip, contribute to a positive mood, reduce feelings of irritability, and enhance memory, learning, and problem-solving skills.8.2 However, the amount at which naps are beneficial depends on many individual factors, including the duration and quality of the nap, the task being performed, and the individual themselves.

The desire to sleep during the day may be a sign that you are not getting enough sleep at night or are getting low-quality sleep. Studies have shown that adults who take longer naps might have conditions like diabetes, heart disease, and depression.8.3 Another study found that daytime napping causes a higher core temperature, altering one’s nighttime thermoregulation. A high core body temperature impairs one’s ability to fall asleep as well as disrupts REM and deep sleep patterns. The data from this study backed up the claim that sometimes naps are necessary due to poor quality or quantity of sleep, and the occasional nap is okay, but it is best not to make it a habit, as naps can be unnecessary when you are getting enough sleep at night.8.4

If you need to take a nap, it is best to do so earlier in the afternoon when your body experiences a natural tiredness, around 2 p.m.8.5 When you nap in the morning, the sleep is primarily composed of non-REM (NREM) sleep. As your sleep drive increases throughout the day, an evening nap will be mainly deep sleep, making it harder to fall asleep that night.8.6 Studies suggest that a brief 20-minute nap can help you feel recharged without the effects of sleep inertia, and due to its short duration, it is less likely to interfere with nighttime sleep.8.7

Children and Sleep

Sleep plays an important part in children’s developing minds, with research showing that children who get insufficient sleep have less grey matter, specifically in certain areas of the brain that are responsible for attention, memory, and control9.2  Not getting enough sleep can have also have long-term effects on academic performance and mental health.9.3 One study found that first-year college students who receive less than six hours of sleep show a decline in their academic performance, in addition to finding that each hour of sleep lost corresponded to a 0.07 decrease in their GPA at the end of their term.9.4 In relation to mental health, while there are multiple factors causing 40 percent of high-school students to report having persistent feelings of sadness and hopelessness, it has been found that sleep is a major culprit.9.5

Sleep loss in adolescence is also correlated with increased occurrence of riskier behaviors including substance abuse, mental health problems, and car crashes to name a few.9.6 For example, adolescents who reported getting 6 hours of sleep per night were three times more likely to partake in substance use compared to those who got 8 or 9 hours of sleep per night.9.7 Another study by the state of North Carolina found that 55% of all asleep-behind-the-wheel crashes were caused by drivers under the age of 25.9.8

Children’s sleep needs vary based on their age. Because children are still growing and developing, they require more sleep than adults.

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It is important to remember that the amount of sleep children are getting is just as important as the quality of sleep they are getting. Here are some tips for helping get high-quality sleep.

Sleep Throughout Your Life

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Sleep and Risk

“It is a common experience that a problem difficult at night is resolved in the morning after the committee of sleep has worked on it.” – John Steinbeck, American Writer

Studies have observed the slowing of cognitive processing when an individual is sleep deprived. Since sleep deprivation interferes with the functioning of certain brain areas and impaired cognitive performance,11.1 it can lead to a decrease in decision-making skills, have a harder time dealing with co-workers, have a higher rate of impulsivity, and are found to react negatively when things do not go their way.11.2

Under the effects of partial sleep loss, individuals who usually are more reflective and cautious become more impulsive and prone to risk-taking during decision-making.11.3 One study found that a group of sleep-deprived individuals scored 63.15 on the Barrat Impulsiveness Scale (a questionnaire examining impulsivity) whereas nonaffected controls scored as less impulsive at 57.94.11.4 The reason why missing sleep, both long-term and short-term, is risky is because it is hard for an individual to recognize that they are impaired, and when they do it is too late.

 

Many working environments, specifically those that pose a greater risk of safety, have requirements when it comes to sleep. The US Federal Aviation Administration (FAA) states that “[f]atigue continues to be one of the most treacherous hazards to flight safety, as it may not be apparent to a pilot until serious errors are made.”11.5 One FAA regulation states that flight crew members must have a 10-hour rest period (time off duty) with a minimum of 8 uninterrupted hours of sleep in order to be fit for duty.11.6

Even in everyday life, being sleep-deprived can be risky. For example, according to the CDC, drowsy driving was involved in 91,000 crashes in 2017, which resulted in 50,000 injuries and nearly 800 deaths. However, many state these numbers are underestimated, and over 6,000 fatal crashes involving drowsy drivers each year. 11.7 One study found that 55% of all drowsy driving crashes were caused by drivers under the age of 25.11.8 Everyday sleep deprivation, or just missing an hour of sleep each night, causes cognitive impairments, including reaction time, problem-solving skills, and attention and concentration. This can lead to minor and major disasters in all occupations.11.9

Sleep Inertia

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According to the CDC, “Sleep inertia is a temporary disorientation and decline in performance and/or mood after awakening from sleep. People can show up to a 41% reduction in performance after waking 12.2 including a slowed reaction time, poorer short-term memory, and slower speed of thinking, reasoning, remembering, and learning”.12.3 Sleep inertia occurs after waking up from a nap or from your nightly sleep and can last anywhere from 30 to 60 minutes.12.4

Since sleep inertia makes you act disoriented and a bit out of it, it is important to wait for the grogginess to clear up before performing any risky tasks or making big decisions. One study found that chewing 100 mg of caffeinated gum when waking up from a nap showed improved performance on a psychomotor vigilance task (a measure of behavioral alertness and vigilance) 12-18 minutes after a nap compared to those who took a placebo.12.5 You can also experience sleep inertia after a nap, which is why it is especially important to keep naps around 10 to 20 minutes in the early afternoon, as well as waiting 30 minutes after for sleep inertia to wear off. Some find that consuming caffeine before a nap is helpful in combating post-nap sleep inertia since it takes about 30 minutes to take effect.12.6

The Cost of Sleep

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The sleep-assistance industry is booming, including pills, products, medical devices, mattresses, and sleep consultants. Anything under the stars advertised to help you fall asleep and stay asleep better is a part of the sleep industry. The global sleep aid market is expected to reach around 131.35 billion USD by 2032.13.2

We love the idea of a quick fix, and younger consumers especially have faith in products to help quickly fix problems. Many young adults jump back and forth between energy drinks to stay alert and sleep aids to help them fall asleep. Finding remedies also allows us to feel we have control over our sleep and the problem rather than just standing by.13.3 Before spending money on sleep aids, try some of the tips below.

Tips To Help Have a Good Night’s Sleep

Further Readings and Resources

A Brief History of Sleep

The Stages of Sleep

Why Are We Losing Sleep?

Sleep and Our Body

Hypertension:

Diabetes:

Diet and Weight: 

Mortality: 

Health Consequences:

Sleep and Our Mind

Memory/Learning:

Productivity:

Reaction Time:

Social:

Emotions:

Sleep Debt

Social Jetlag

Naps

Children and Sleep

Sleep and Risk

Sleep Inertia

The Cost of Sleep

Tips to Help Have a Good Night Sleep

Cited Resources