Sleep deprivation is a condition that occurs if you don't get enough sleep. Sleep deficiency is a broader concept. It occurs if you have one or more of the following:

• You don't get enough sleep (sleep deprivation)
• You sleep at the wrong time of day
• You don't sleep well or get all the different types of sleep your body needs
• You have a sleep disorder that prevents you from getting enough sleep or causes poor-quality sleep

Sleeping is a basic human need, like eating, drinking, and breathing. Like these other needs, sleeping is vital for good health and well-being throughout your lifetime.

According to the Centers for Disease Control and Prevention, about 1 in 3 adults in the United States reported not getting enough rest or sleep every day.

Nearly 40% of adults report falling asleep during the day without meaning to at least once a month. Also, an estimated 50 to 70 million Americans have chronic, or ongoing, sleep disorders.

Sleep deficiency can lead to physical and mental health problems, injuries, loss of productivity, and even a greater likelihood of death. To understand sleep deficiency, it helps to understand what makes you sleep and how it affects your health.

Sleep deficiency can interfere with work, school, driving, and social functioning. You might have trouble learning, focusing, and reacting. Also, you might find it hard to judge other people's emotions and reactions. Sleep deficiency also can make you feel frustrated, cranky, or worried in social situations.

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 deficiency is linked to many chronic health problems, including heart disease, kidney disease, high blood pressure, diabetes, stroke, obesity, and depression.

Sleep deficiency is also linked to a higher chance of injury in adults, teens, and children. For example, sleepiness while driving (not related to alcohol) is responsible for serious car crash injuries and death. In older adults, sleep deficiency may be linked to a higher chance of falls and broken bones.

Sleep deficiency has also played a role in human mistakes linked to tragic accidents, such as nuclear reactor meltdowns, grounding of large ships, and plane crashes.

A common myth is that people can learn to get by on little sleep with no negative effects. However, research shows that getting enough quality sleep at the right times is vital for mental health, physical health, quality of life, and safety.

Many factors play a role in preparing your body to fall asleep and wake up. You have an internal "body clock" that manages when you're awake and when your body is ready for sleep.

Your body clock

The body clock typically has a 24-hour repeating rhythm (called the circadian rhythm). Two processes interact to control this rhythm.

• The first is a pressure to sleep that builds with every hour that you're awake. This drive for sleep peaks in the evening when most people fall asleep. A compound called adenosine seems to be one factor linked to this drive for sleep. While you're awake, the level of adenosine in your brain continues to rise. The increasing level of this compound signals a shift toward sleep. While you sleep, your body breaks down adenosine.
• A second process involves your internal body clock. This clock is in sync with certain cues in the environment. Light, darkness, and other cues help determine when you feel awake and when you feel sleepy.

For example, light signals received through your eyes tell your brain that it is daytime. This area of your brain helps align your body clock with periods of the day and night.

Hormones

Your body releases chemicals in a daily rhythm that your body clock controls.

Melatonin

When it gets dark, your body releases a hormone called melatonin. Melatonin signals your body that it's time to prepare for sleep, and it helps you feel sleepy.

The amount of melatonin in your bloodstream peaks as the evening passes. Researchers believe this peak is an important part of preparing your body for sleep.

Exposure to bright artificial light late in the evening can disrupt this process, making it hard to fall asleep. Examples of bright artificial light include the light from a TV screen, computer screen, or a very bright alarm clock.

Cortisol

As the sun rises, your body releases cortisol. This hormone naturally prepares your body to wake up.

The rhythm and timing of the body clock change with age. Teens fall asleep later at night than younger children and adults. One reason for this is because melatonin is released and peaks later in the 24-hour cycle for teens. As a result, it's natural for many teens to prefer later bedtimes at night and sleep later in the morning than adults.

People also need more sleep early in life when they're growing and developing. For example, newborns may sleep more than 16 hours a day, and preschool-age children need to take naps.

Young children tend to sleep more in the early evening. Teens tend to sleep more in the morning. Also, older adults tend to go to bed earlier and wake up earlier.

The patterns and types of sleep also change as people mature. For example, newborn infants spend more time in REM (rapid eye movement) sleep. Dreaming typically occurs during REM sleep.

The amount of deep or slow-wave sleep (non-REM sleep) peaks in early childhood and then drops sharply after puberty. It continues to decline as people age.

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 hormonesthat 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.
• Decreasesyour risk of health problems, including heart disease, high blood pressure, obesity, and stroke.

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.

Beta-amyloid is a metabolic waste product that’s found in the fluid between brain cells (neurons). A build-up of beta amyloid is linked to impaired brain function and Alzheimer’s disease. In Alzheimer’s disease, beta-amyloid clumps together to form amyloid plaques, which hinder communication between neurons.

Impaired sleep has been associated with Alzheimer’s disease. Studies suggest that sleep plays a role in clearing beta-amyloid out of the brain. Moreover, lack of sleep has been shown to elevate brain beta-amyloid levels in mice. Less is known about the impact of sleep deprivation on beta-amyloid levels in people.

To investigate the possible link between beta-amyloid and sleep in people, lead author Dr. Ehsan Shokri-Kojori, in a team led by Drs. Nora D. Volkow and Gene-Jack Wang of NIH’s National Institute on Alcohol Abuse and Alcoholism (NIAAA), used positron emission tomography (PET) to scan the brains of 20 healthy participants, aged 22 to 72. To measure beta-amyloid they used a radiotracer called ¹⁸F-florbetaben that has been shown to bind beta-amyloid. Results were published online on April 9, 2018, in the Proceedings of the National Academy of Sciences.

The researchers scanned participants’ brains after getting a full night’s rest and after a night of sleep deprivation (about 31 hours without sleep). Beta-amyloid increased about 5% in the participants’ brains after losing a night of sleep. These changes occurred in brain regions that included the thalamus and hippocampus, which are especially vulnerable to damage in the early stages of Alzheimer’s disease.

The scientists also found that study participants with larger increases in beta-amyloid reported worse mood after sleep deprivation. These findings support other studies that have found that the hippocampus and thalamus play a role in mood disorders.

“Even though our sample was small, this study demonstrated the negative effect of sleep deprivation on beta-amyloid burden in the human brain,” Shokri-Kojori says. “Future studies are needed to assess the generalizability to a larger and more diverse population.”

“This research provides new insight about the potentially harmful effects of a lack of sleep on the brain and has implications for better characterizing the pathology of Alzheimer's disease,” says Dr. George F. Koob, director of NIAAA.

More studies are needed to identify the precise biological mechanism underlying the observed increase in beta-amyloid. It’s also important to note that the link between sleep disorders and Alzheimer’s risk is thought to go both ways. Elevated beta-amyloid may also lead to trouble sleeping.

The amount of sleep you need each day will change over the course of your life. Although sleep needs vary from person to person, the chart below shows general recommendations for different age groups. This table reflects American Academy of Sleep Medicine (AASM) recommendations that the American Academy of Pediatrics (AAP) has endorsed.

If you regularly lose sleep or choose to sleep less than needed, the sleep loss adds up. The total sleep lost is called your sleep debt. For example, if you lose 2 hours of sleep each night, you'll have a sleep debt of 14 hours after a week.

Some people nap to deal with sleepiness. Naps may give a short-term boost in alertness and performance. However, napping doesn't supply all the other benefits of nighttime sleep, so you can't really make up for lost sleep.

Some people sleep more on their days off than on workdays. They also may go to bed and wake up later on days off.

Sleeping more on days off might be a sign that you aren't getting enough sleep. Although extra sleep on days off might help you feel better, it can upset your body's sleep-wake rhythm.

Sleep deficiency, which includes sleep deprivation, affects people of all ages, races, and ethnicities. Certain groups of people may be more likely to be sleep deficient, including people who:

• Have limited time for sleep, such as caregivers or people working long hours or more than one job
• Have schedules that conflict with their internal body clocks, such as shift workers, first responders, teens who have early school schedules, or people who must travel for work
• Make lifestyle choices that prevent them from getting enough sleep, such as taking medicine to stay awake, misusing alcohol or drugs, or not leaving enough time for sleep
• Have undiagnosed or untreated medical problems, such as stress, anxiety, or sleep disorders
• Have medical conditions or take medicines that interfere with sleep

If your job or daily routine limits your ability to get enough sleep or sleep at the right times, talk with your doctor. You also should talk with your doctor if you sleep more than 8 hours a night, but don't feel well rested. You may have a sleep disorder or other health problem.

Doctors might not identify sleep problems during routine office visits because patients are awake, so let your doctor know if you think you might have a sleep problem.

For example, talk with your doctor if you often feel sleepy during the day, don't wake up feeling refreshed and alert, or are having trouble adapting to shift work.

To get a better sense of your sleep problem, your doctor will ask you about your sleep habits. Before you see the doctor, think about how to describe your problems, including:

• How often you have trouble sleeping and how long you've had the problem
• When you go to bed and get up on workdays and days off
• How long it takes you to fall asleep, how often you wake up at night, and how long it takes you to fall back asleep
• Whether you snore loudly and often or wake up gasping or feeling out of breath
• How refreshed you feel when you wake up, and how tired you feel during the day
• How often you doze off or have trouble staying awake during routine tasks, especially driving

Your doctor also may ask questions about your personal routine and habits. For example, they may ask about your work and exercise routines. Your doctor also may ask whether you use caffeine, tobacco, alcohol, or any medicines (including over-the-counter medicines).

Sleep diary

To help your doctor, consider keeping a sleep diary for a few weeks.

• Write down when you go to sleep, wake up, and take naps. (For example, you might note: Went to bed at 10 a.m.; woke up at 3 a.m. and couldn't fall back asleep; napped after work for 2 hours.)
• Write down how much you sleep each night, how alert and rested you feel in the morning, and how sleepy you feel at various times during the day.

Sleep studies

Doctors can diagnose some sleep disorders by asking questions about sleep schedules and habits and by getting information from sleep partners or parents. To diagnose other sleep disorders, doctors also use the results from sleep studies and other medical tests.

Sleep studies, also called polysomnography, are painless tests that measure how well you sleep and how your body responds to sleep problems. They are also used to help your doctor diagnose sleep disorders.

The most common type of sleep studies records brain waves and monitor your heart rate, breathing, and the oxygen level in your blood during a full night of sleep.

Other ways to study your sleep include:

• Multiple sleep latency tests measure how quickly you fall asleep during a series of daytime naps and use sensors to record your brain activity and eye movements.
• A daytime maintenance of wakefulness test measures your ability to stay awake and alert.
• Activity monitors help doctors see how much you sleep and how well you sleep. They are worn at home for several days or sometimes weeks.

Sleep tests can help your doctor diagnose sleep-related breathing disorders such as sleep apnea, sleep-related seizure disorders, sleep-related movement disorders, and sleep disorders that cause extreme daytime tiredness such as narcolepsy. Doctors also may use sleep tests to help diagnose or rule out restless legs syndrome.

Your doctor will determine whether you need your sleep test at a sleep center or if you can do it at home with a portable device. Sleep tests at a sleep center usually last overnight. Removable sensors will be placed on your scalp, face, eyelids, chest, limbs, and a finger. These sensors record your brain waves, heart rate, breathing effort and rate, oxygen levels, and muscle movements before, during, and after sleep. There is a small risk of irritation from the sensors, but this will go away after they are removed.

Your doctor may do a physical exam to rule out other medical problems that might interfere with sleep. You may need blood tests to check for thyroid problems or other conditions that can cause sleep problems.

If your doctor diagnoses you with a sleep disorder, they may talk to you about healthy sleep habits. Your treatment options will depend on which type you have.

• For sleep apnea, the goals of treatment are to help keep your airways open during sleep. This may include a CPAP machine or other breathing devices, therapy, or surgery.
• For narcolepsy and insomnia, treatment options include medicines and behavior changes.

A good night’s sleep is vital for your health. Sleep helps your brain work properly. A lack of adequate sleep over time can also lead to disruptions in metabolism. These disruptions increase the risk for obesity and diabetes.

Experts recommend that adults get at least 7 hours of sleep every night. But studies have found that about a third of adults regularly get less than 7 hours of sleep. Some people try to make up for these deficits by sleeping more on their days off work. Whether this strategy can make up for the damage done by work-week sleep deprivation wasn't known.

To study the effects of make-up sleep on metabolism, researchers led by Dr. Kenneth Wright, Jr. from the University of Colorado brought 36 healthy men and women into their sleep lab for two weeks. After allowing three nights of normal sleep, the researchers split the participants into three groups.

The first group was allowed to continue sleeping up to 9 hours a night. The second was allowed a maximum of 5 hours sleep a night for the length of the study. The third modeled “weekend recovery sleep.” They slept a maximum of 5 hours a night for 5 days, were allowed to sleep in for 2 days, then returned to sleep deprivation for another 2 days.

The researchers measured eating patterns, weight gain, and changes in insulin sensitivity (the body’s ability to use insulin properly and control blood glucose levels). The study was funded by NIH’s National Heart, Lung, and Blood Institute (NHLBI), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), and others. Results were published on February 28, 2019, in Current Biology.

Consistent sleep deprivation quickly distorted metabolism. Compared to people who slept normally, those who only slept 5 hours a night snacked more after dinner and gained an average of about 3 pounds during the study. Their bodies’ sensitivity to insulin decreased by 13% over the two-week period.

Recovery sleep didn’t provide any benefit over continuous sleep deprivation. Though they were allowed to sleep as much as they wanted over a weekend, participants in the recovery sleep group only managed to get an average of 3 hours extra sleep over 2 nights.

The extra sleep on the weekend actually disrupted the participants’ body rhythms when they returned to sleep deprivation. Following the recovery sleep period, they were more likely to wake up when their natural body rhythm was still promoting sleep.

Participants in the recovery sleep group were less likely to snack at night during the recovery period. However, they reverted to late-night eating as soon as sleep deprivation began again. They also gained an average of about 3 pounds during the study and experienced a 27% decrease in insulin sensitivity. Notably, liver and muscle insulin sensitivity were reduced only in the weekend recovery sleep group.

“The key take-home message from this study is that… weekend recovery or catch-up sleep does not appear to be an effective countermeasure strategy to reverse sleep loss induced disruptions of metabolism,” Wright says.

—by Sharon Reynolds

You can take steps to improve your sleep habits. First, make sure that you give yourself enough time to sleep. With enough sleep each night, you may find that you're happier and more productive during the day.

Sleep is often the first thing that busy people squeeze out of their schedules. Making time to sleep will help you protect your health and well-being now and in the future.

To improve your sleep habits, it also may help to:

• Go to bed and wake up at the same time every day. For children, have a set bedtime and a bedtime routine. Don't use the child's bedroom for timeouts or punishment.
• Try to keep the same sleep schedule on weeknights and weekends. Limit the difference to no more than about an hour. Staying up late and sleeping in late on weekends can disrupt your body clock's sleep-wake rhythm.
• Use the hour before bed for quiet time. Avoid intense exercise and bright artificial light, such as from a TV or computer screen. The light may signal the brain that it's time to be awake.
• Avoid heavy or large meals within a few hours of bedtime. (Having a light snack is okay.) Also, avoid alcoholic drinks before bed.
• Avoid nicotine (for example, cigarettes) and caffeine (including caffeinated soda, coffee, tea, and chocolate). Nicotine and caffeine are stimulants, and both substances can interfere with sleep. The effects of caffeine can last up to 8 hours. So, a cup of coffee in the late afternoon can make it hard for you to fall asleep at night.
• Spend time outside every day (when possible) and be physically active.
• Keep your bedroom quiet, cool, and dark (a dim night light is fine, if needed).
• Take a hot bath or use relaxation techniques before bed.

Napping during the day may boost your alertness and performance. However, if you have trouble falling asleep at night, limit naps or take them earlier in the afternoon. Adults should nap for no more than 20 minutes.

Napping in preschool-age children is normal and promotes healthy growth and development.

Strategies for shift workers

Some people have schedules that conflict with their internal body clocks. For example, shift workers may have trouble getting enough sleep. This can affect how they feel mentally and physically.

If you're a shift worker, you may find it helpful to:

• Take naps and raise the amount of time available for sleep
• Keep the lights bright at work
• Limit shift changes so your body clock can adjust
• Limit caffeine use to the first part of your shift
• Remove sound and light distractions in your bedroom during daytime sleep (for example, use light-blocking curtains)

If you're still not able to fall asleep during the day or have problems adapting to a shift-work schedule, talk with your doctor about other options to help you sleep.