Sleeptime Stories: Your Sleep Questions Answered

1. Sleep Overview
2. What Is Sleep?
3. What Makes You Sleep?
4. What Does Sleep Do For You?
5. View All

Get a Good’s Night Rest

Get Your Questions About Sleep Answered So You Can Finally Rest

Think of everything you do during your day. Try to guess which activity is so important you should devote one-third of your time to doing it. Probably the first things that come to mind are working, spending time with your family, or pursuing leisure activities. But there’s something else you should be doing about one-third of your time – sleeping.

Many people view sleep as merely a “down time” when their brain shuts off and their body rests. In a rush to meet work, school, family, or household responsibilities, people cut back on their sleep, thinking it won’t be a problem, because all of these other activities seem much more important. But research reveals that a number of vital tasks carried out during sleep help to maintain good health and enable people to function at their best.

While you sleep, your brain is hard at work forming the pathways necessary for learning and creating memories and new insights.

Without enough sleep, you can’t focus and pay attention or respond quickly. A lack of sleep may even cause mood problems. In addition, growing evidence shows that a chronic lack of sleep increases the risk for developing obesity, diabetes, cardiovascular disease, and infections.

Despite the mounting support for the notion that adequate sleep, like adequate nutrition and physical activity, is vital to our wellbeing, people are sleeping less. The nonstop “24/7″ nature of the world today encourages longer or nighttime work hours and offers continual access to entertainment and other activities. To keep up, people cut back on sleep. A common myth is that people can learn to get by on little sleep (such as less than 6 hours a night) with no adverse consequences. Research suggests, however, that adults need at least 7-8 hours of sleep each night to be well rested. Indeed, in 1910, most people slept 9 hours a night. But recent surveys show the average adult now sleeps less than 7 hours a night, and more than one-third of adults report daytime sleepiness so severe that it interferes with work and social functioning at least a few days each month. As many as 70 million Americans may be affected by chronic sleep loss or sleep disorders, at an annual cost of $16 billion in health care expenses and $50 billion in lost productivity.

What happens when you don’t get enough sleep? Can you make up for lost sleep during the week by sleeping more on the weekends? How does sleep change as you become older? Is snoring a problem? How can you tell if you have a sleep disorder? Read on to find the answers to these questions and to better understand what sleep is and why it is so necessary. Learn about common sleep myths and practical tips for getting adequate sleep, coping with jet lag and nighttime shift work, and avoiding dangerous drowsy driving.

Many common sleep disorders go unrecognized and thus are not treated. This booklet also gives the latest information on sleep disorders such as insomnia, sleep apnea, restless legs syndrome, narcolepsy, and parasomnias.

What is Sleep?

Sleep was long considered just a uniform block of time when you are not awake. Thanks to sleep studies done over the past several decades, it is now known that sleep has distinct stages that cycle throughout the night in predictable patterns. How well rested you are and how well you function depend not just on your total sleep time but on how much of the various stages of sleep you get each night.

Your brain stays active throughout sleep, and each stage of sleep is linked to a distinctive pattern of electrical activity known as brain waves.

Sleep is divided into two basic types: rapid eye movement (REM) sleep and non-REM sleep (with four different stages). Typically, sleep begins with non-REM sleep.

In stage 1 non-REM sleep, you sleep lightly and can be awakened easily by noises or other disturbances. During this first stage of sleep, your eyes move slowly, and your muscle activity slows. You then enter stage 2 non-REM sleep, when your eye movements stop.

Your brain shows a distinctive pattern of slower brain waves with occasional bursts of rapid waves.

When you progress into stage 3 non-REM sleep, your brain waves become even slower, although they are still punctuated by smaller, faster waves. By stage 4 non-REM sleep, the brain produces extremely slow waves almost exclusively. Stages 3 and 4 are considered deep sleep, during which it is very difficult to be awakened.

Children who wet the bed or sleep walk tend to do so during stages 3 or 4 of non-REM sleep. Deep sleep is considered the “restorative” part of sleep that is necessary for feeling well rested and energetic during the day.

During REM sleep, your eyes move rapidly in various directions, even though your eyelids remain closed. Your breathing also becomes more rapid, irregular, and shallow, and your heart rate and blood pressure increase. Dreaming typically occurs during REM sleep. During this type of sleep, your arm and leg muscles are temporarily paralyzed so that you cannot “act out” any dreams that you may be having.

The first period of REM sleep you experience usually occurs about an hour to an hour and a half after falling asleep. After that, the sleep stages repeat themselves continuously while you sleep. As the night progresses, REM sleep time becomes longer, while time spent in non-REM sleep stages 3 and 4 becomes shorter. By morning, nearly all your sleep time is spent in stages 1 and 2 of non-REM sleep and in REM sleep. If REM sleep is disrupted during one night,

REM sleep time is typically longer than normal in subsequent nights until you catch up. Overall, almost one-half your total sleep time is spent in stages 1 and 2 non-REM sleep and about one-fifth each in deep sleep (stages 3 and 4 of non-REM sleep) and REM sleep. In contrast, infants spend half or more of their total sleep time in REM sleep. Gradually, as they mature, the percentage of total sleep time they spend in REM progressively decreases to reach the one-fifth level typical of later childhood and adulthood.

Why people dream and why REM sleep is so important are not well understood. It is known that REM sleep stimulates the brain regions used in learning and the laying down of memories. Animal studies suggest that dreams may reflect the brain’s sorting and selectively storing important new information acquired during wake time. While this information is processed, the brain might revisit scenes from the day while pulling up older memories. This process may explain why childhood memories can be interspersed with more recent events during dreams. Studies show, however, that other stages of sleep besides REM are also needed to form the pathways in the brain that enable us to learn and remember.

What Makes You Sleep?

Although you may put off going to sleep in order to squeeze more activities into your day, eventually your need for sleep becomes overwhelming and you are forced to get some sleep. This daily drive for sleep appears to be due, in part, to a compound known as adenosine. This natural chemical builds up in your blood as time awake increases. While you sleep, your body breaks down the adenosine. Thus, this molecule may be what your body uses to keep track of lost sleep and to trigger sleep when needed. An accumulation of adenosine and other factors might explain why, after several nights of less than optimal amounts of sleep, you build up a sleep debt that you must make up by sleeping longer than normal. Because of such built-in molecular feedback, you can’t adapt to getting less sleep than your body needs. Eventually, a lack of sleep catches up with you.

The time of day when you feel sleepy and go to sleep is also governed by your internal “biological clock” and environmental cues-the most important being light and darkness. Your biological clock is actually a tiny bundle of cells in your brain that responds to light signals received through your eyes. When darkness falls, the biological clock triggers the production of the hormone melatonin.

This hormone makes you feel drowsy as it continues to increase during the night. Because of your biological clock, you naturally feel the sleepiest between midnight and 7 a.m. You may also feel a second and milder daily “low” in the mid-afternoon between 1 p.m. and 4 p.m. At that time, another rise occurs in melatonin production and might make you feel sleepy.

Your biological clock makes you the most alert during daylight hours and the most drowsy in the early morning hours. Consequently, most people do their best work during the day. Our 24/7 society, however, demands that some people work at night. Nearly one-quarter of all workers work shifts that are not during the daytime, and more than two-thirds of these workers have problem sleepiness and/or difficulty sleeping. Because their work schedules are at odds with powerful sleep-regulating cues like sunlight, night shift workers often find themselves drowsy at work, and they have difficulty falling or staying asleep during the daylight hours when their work schedules require them to sleep.

The fatigue experienced by night shift workers can be dangerous. Major industrial accidents – such as the Three Mile Island and Chernobyl nuclear power plant accidents and the Exxon Valdez oil spill – have been caused, in part, by mistakes made by overly tired workers on the night shift or an extended shift.

Night shift workers also are at greater risk of being in car crashes when they drive home from work. One study found that one-fifth of night shift workers had a car crash or a near miss in the preceding year because of sleepiness on the drive home from work. Night shift workers are also more likely to have physical problems, such as heart disease, digestive disturbances, and infertility, as well as emotional problems. All of these problems may be related, at least in part, to the workers’ chronic sleepiness.

Other factors can also influence your need for sleep, including your immune system’s production of cellular hormones called cytokines. These compounds are made in large quantities in response to certain infectious diseases or chronic inflammation and may prompt you to sleep more than usual. The extra sleep may help you conserve the resources needed to fight the infection. Recent studies confirm that being well rested improves the body’s responses to infection.

People are creatures of habit, and one of the hardest habits to break is the natural wake and sleep cycle. A number of physiological factors conspire to help you sleep and wake up at the same times each day. Consequently, you may have a hard time adjusting when you travel across time zones. The light cues outside and the clocks in your new location may tell you it is 8 a.m. and you should be active, but your body is telling you it is more like 4 a.m. and you should sleep. The end result is jet lag-sleepiness during the day, difficulty falling or staying asleep at night, poor concentration, confusion, nausea, and general malaise and irritability.

What Does Sleep Do For You?

A number of tasks vital to health and quality of life are linked to sleep, and these tasks are impaired when you are sleep deprived.

Learning, Memory, and Mood

Students who have trouble grasping new information or learning new skills are often advised to “sleep on it,” and that advice seems well founded. Recent studies reveal that people can learn a task better if they are well rested. They also can remember better what they learned if they get a good night’s sleep after learning the task than if they are sleep deprived. Volunteers had to sleep at least 6 hours to show improvement in learning, and the amount of improvement was directly tied to how much time they slept. In other words, volunteers who slept 8 hours outperformed those who slept only 6 or 7 hours. Other studies suggest that all the benefits of training for mentally challenging tasks are maximized after a good night’s sleep, rather than immediately following the training or after sleeping for a short period overnight.

Many well-known artists and scientists claim to have had creative insights while they slept.

Mary Shelley, for example, said the idea for her novel Frankenstein came to her in a dream. Although it has not been shown that dreaming is the driving force behind innovation, one study suggests that sleep is needed for creative problem solving. In that study, volunteers were asked to perform a memory task and then were tested 8 hours later. Those who were allowed to sleep for 8 hours immediately after receiving the task and before being tested were much more likely to find a creative way of simplifying the task and improving their performance compared to those who were awake the entire 8 hours before being tested.

Exactly what happens during sleep to improve our learning, memory, and insight isn’t known. Experts suspect, however, that while people sleep, they form or reinforce the pathways of brain cells needed to perform these tasks. This process may explain why sleep is needed for proper brain development in infants.

Not only is a good night’s sleep required to form new learning and memory pathways in the brain, but sleep is also necessary for those pathways to work up to speed. Several studies show that lack of sleep causes thinking processes to slow down. Lack of sleep also makes it harder to focus and pay attention. Lack of sleep can make you more easily confused. Studies also find a lack of sleep leads to faulty decision making and more risk taking. A lack of sleep slows down your reaction time, which is particularly significant to driving and other tasks that require quick response. When people who lack sleep are tested by using a driving simulator, they perform just as poorly as people who are drunk. The bottom line is: not getting a good night’s sleep can be dangerous!

Even if you don’t have a mentally or physically challenging day ahead of you, you should still get enough sleep to put yourself in a good mood. Most people report being irritable, if not downright unhappy, when they lack sleep. People who chronically suffer from a lack of sleep, either because they do not spend enough time in bed or because they have an untreated sleep disorder, are at greater risk of developing depression. One group of people who usually don’t get enough sleep is mothers of newborns. Some experts think depression after childbirth (postpartum blues) is caused, in part, by a lack of sleep.

Your Heart

Sleep gives your heart and vascular system a much-needed rest.

During non-REM sleep, your heart rate and blood pressure progressively slow as you enter deeper sleep. During REM sleep, your heart rate and blood pressure have boosted spikes of activity. Overall, however, sleep reduces your heart rate and blood pressure by about 10 percent.

If you don’t get enough sleep, this nightly dip in blood pressure, which appears to be important for good cardiovascular health, may not occur. According to several studies, if your blood pressure does not dip during sleep, you are more likely to experience strokes, chest pain known as angina, an irregular heartbeat, and heart attacks. You are also more likely to develop congestive heart failure, a condition in which fluid builds up in the body because the heart is not pumping sufficiently. Failure to experience the normal dip in blood pressure during sleep can be related to insufficient sleep time, an untreated sleep disorder, or other factors. African

Americans, for example, tend not to have as much of a dip in blood pressure during sleep. This difference may help to explain why they are more likely than Caucasians to have serious cardiovascular disease.

A lack of sleep also puts your body under stress and may trigger the release of more adrenaline, cortisol, and other stress hormones during the day. These hormones contribute to your blood pressure not dipping during sleep, thereby increasing the risk for heart disease. Inadequate sleep may also negatively affect your heart and vascular system by the increased production of certain proteins thought to play a role in heart disease. For example, some studies find that people who chronically do not get enough sleep have higher blood levels of C-reactive protein. Higher levels of this protein may suggest a greater risk of developing hardening of the arteries (atherosclerosis).

Your Hormones

When you were young, your mother may have told you that you need to get enough sleep to grow strong and tall. She may have been right! Deep sleep triggers more release of growth hormone, which fuels growth in children and boosts muscle mass and the repair of cells and tissues in children and adults. Sleep’s effect on the release of sex hormones also encourages puberty and fertility. Consequently, women who work at night and tend to lack sleep are, therefore, more likely to have trouble conceiving or to miscarry.

Your mother also probably was right if she told you that getting a good night’s sleep on a regular basis would help keep you from getting sick and help you get better if you do get sick. During sleep, your body creates more cytokines-cellular hormones that help the immune system fight various infections. Lack of sleep can reduce the ability to fight off common infections. Research also reveals that a lack of sleep can reduce the body’s response to the flu vaccine.

For example, sleep-deprived volunteers given the flu vaccine produced less than half as many flu antibodies as those who were well rested and given the same vaccine.

Although lack of exercise and other factors are important contributors, the current epidemic of diabetes and obesity appears to be related, at least in part, to chronically getting inadequate sleep.

Evidence is growing that sleep is a powerful regulator of appetite, energy use, and weight control. During sleep, the body’s production of the appetite suppressor leptin increases, and the appetite stimulant grehlin decreases. Studies find that the less people sleep, the more likely they are to be overweight or obese and prefer eating foods that are higher in calories and carbohydrates. People who report an average total sleep time of 5 hours a night, for example, are much more likely to become obese compared to people who sleep 7-8 hours a night.

A number of hormones released during sleep also control the body’s use of energy. A distinct rise and fall of blood sugar levels during sleep appears to be linked to sleep stage. Not getting enough sleep overall or enough of each stage of sleep disrupts this pattern. One study found that, when healthy young men slept only 4 hours a night for 6 nights in a row, their insulin and blood sugar levels mimicked those seen in people who were developing diabetes. Another study found that women who slept less than 7 hours a night were more likely to develop diabetes over time than those who slept between 7 and 8 hours a night.

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