By the National Institutes of Health/February 02, 2011
Anyone who has ever felt tired in the morning or dozed off in a meeting knows that sleep is important. In fact, getting enough is vital to your well-being. Here's why you need more shut-eye, along with tips to help you get it...
Until the 1950s, most people thought of sleep as a passive, dormant part of our daily lives. We now know that our brains are very active while we sleep. In fact, getting enough shut-eye affects our daily functioning and our physical and mental health in ways we're just beginning to understand.
The amount of sleep each person needs depends on many factors, including age. Infants generally require about 16 hours a day, while teenagers need about 9 hours.
For most adults, 7-8 hours a night appears to be the best amount of sleep, although some may need as few as 5 or as many as 10. Women in the first three months of pregnancy often need several more hours of sleep than usual.
The amount of sleep a person needs also increases if she's been deprived of sleep in previous days. Getting too little sleep creates a "sleep debt," which is much like being overdrawn at a bank. Eventually, your body will demand that the debt be repaid.
People tend to sleep more lightly and for shorter time spans as they get older, although they generally need about the same amount of sleep as they needed in early adulthood.
About half of all people over 65 have frequent sleeping problems, such as insomnia, and deep sleep stages in many elderly people often become very short or stop completely. This change may be a normal part of aging, or it may result from medical problems that are common in elderly people and from the medications and other treatments for those problems.
The Importance of Sleeping Enough
We don't seem to adapt to getting less sleep than we need. While we may get used to a sleep-depriving schedule, our judgment, reaction time and other functions are still impaired. Yet the widespread practice of "burning the candle at both ends" has created so much sleep deprivation that what is really abnormal sleepiness is now almost the norm.
Experts say that if you feel drowsy during the day, even during boring activities, you haven't had enough sleep. If you routinely fall asleep within five minutes of lying down, you probably have severe sleep deprivation, possibly even a sleep disorder.
Microsleeps, or very brief episodes of sleep in an otherwise awake person, are another mark of sleep deprivation. In many cases, people are not aware that they are experiencing microsleeps.
Many studies make it clear that sleep deprivation is dangerous. Sleep-deprived people who use a driving simulator or perform hand-eye coordination tests perform as badly as, or worse than, those who are intoxicated.
Driver fatigue is responsible for an estimated 100,000 motor vehicle accidents and 1,500 deaths each year, according to the National Highway Traffic Safety Administration. Since drowsiness is the brain's last step before falling asleep, driving while drowsy can – and often does – lead to disaster.
Sleep deprivation also magnifies alcohol's effects on the body, so a fatigued person who drinks will become much more impaired than someone who is well-rested.
Caffeine and other stimulants can't overcome the effects of severe sleep deprivation. The National Sleep Foundation says that if you have trouble keeping your eyes focused, if you can't stop yawning, or if you can't remember driving the last few miles, you're probably too drowsy to drive safely.
What Does Sleep Do For Us?
Although scientists are still trying to learn exactly why people need sleep, animal studies show that sleep is necessary for survival.
For example, while rats normally live for two to three years, those deprived of rapid eye movement (REM) sleep survive only about five weeks on average, and rats deprived of all sleep stages live only about three weeks. Sleep-deprived rats also develop abnormally low body temperatures and sores on their tail and paws, possibly because their immune systems become impaired.
Sleep appears necessary for our nervous systems to work properly. Too little leaves us drowsy and unable to concentrate the next day. It also leads to impaired memory and physical performance and reduced ability to carry out math calculations. If sleep deprivation continues, hallucinations and mood swings may develop.
Some experts believe sleep gives neurons used while we're awake a chance to shut down and repair themselves. Without it, these brain cells may become so depleted in energy or so polluted with byproducts that they begin to malfunction.
Deep sleep coincides with the release of growth hormones in children and young adults. Many of the body's cells also show increased production and reduced breakdown of proteins during deep sleep.
Since proteins are the building blocks needed for cell growth and for repair of damage from factors like stress and ultraviolet rays, deep sleep may truly be "beauty sleep."
Activity in parts of the brain that control emotions, decision-making processes and social interactions is drastically reduced during deep sleep, suggesting that this type of sleep may help people maintain optimal emotional and social functioning.
Sleep and Disease
Sleep and sleep-related problems play a role in a large number of human disorders and affect almost every field of medicine.
For example, problems like stroke and asthma attacks tend to occur more frequently during the night and early morning, perhaps due to changes in hormones, heart rate and other characteristics associated with sleep.
Sleep also affects some kinds of epilepsy in complex ways. REM (which often accompanies dreaming) seems to help prevent seizures that begin in one part of the brain from spreading to other brain regions, while deep sleep may promote the spread of these seizures. Sleep deprivation also triggers seizures in people with some types of epilepsy.
Neurons that control sleep interact closely with the immune system. As anyone who has had the flu knows, infectious diseases tend to make us feel sleepy. This probably happens because cytokines, chemicals our immune systems produce while fighting an infection, are powerful sleep-inducing chemicals. Sleep may help the body conserve energy and other resources that the immune system needs to mount an attack.
Sleeping problems occur in almost all people with mental disorders, including those with depression and schizophrenia. People with depression, for example, often awaken in the early hours of the morning and find themselves unable to get back to sleep.
The amount of sleep a person gets also strongly influences the symptoms of mental disorders. Sleep deprivation is an effective therapy for people with certain types of depression, while it can actually cause depression in other people.
Extreme sleep deprivation can lead to a seemingly psychotic state of paranoia and hallucinations in otherwise healthy people, and disrupted sleep can trigger episodes of mania (agitation and hyperactivity) in people with manic depression.
Sleeping problems are common in many other disorders as well, including Alzheimer's disease, stroke, cancer and head injury. These issues may arise from changes in the brain regions and neurotransmitters that control sleep, or from the drugs used to control symptoms of other disorders.
In patients who are hospitalized or who receive round-the-clock care, treatment schedules or hospital routines also may disrupt sleep. The old joke about a patient being awakened by a nurse so he could take a sleeping pill contains a grain of truth.
Once sleeping problems develop, they can add to a person's impairment and cause confusion, frustration or depression. Patients who are unable to sleep also notice pain more and may increase their requests for pain medication. Better management of sleeping problems in people with other disorders can improve their health and quality of life.
Tips for a Good Night's Sleep
Set a schedule. Go to bed at a set time each night and get up at the same time each morning. Disrupting this schedule may lead to insomnia. "Sleeping in" on weekends also makes it harder to wake up early on Monday morning because it resets your sleep cycles for a later awakening.
Exercise. Try to exercise 20-30 minutes a day. Daily exercise often helps people sleep, although a workout soon before bedtime may interfere with sleep. For maximum benefit, try to get your exercise about 5-6 hours before going to bed.
Avoid caffeine, nicotine and alcohol. Caffeine acts as a stimulant and keeps people awake. (Sources include coffee, chocolate, soft drinks, non-herbal teas, diet drugs and some pain relievers.) Smokers tend to sleep very lightly and often wake up in the early morning due to nicotine withdrawal. Alcohol robs people of deep sleep and REM sleep and keeps them in the lighter stages of sleep.
Relax before bed. A warm bath, reading or other relaxing routines can make it easier to fall sleep. You can train yourself to associate certain restful activities with sleep and make them part of your bedtime ritual.
Sleep until sunlight. If possible, wake up with the sun, or use very bright lights in the morning. Sunlight helps the body's internal biological clock reset itself each day. Sleep experts recommend exposure to an hour of morning sunlight for people having problems falling asleep.
Don't lie in bed awake. If you can't get to sleep, don't just lie in bed. Do something else, like reading, watching television or listening to music, until you feel tired. The anxiety of being unable to fall asleep can actually contribute to insomnia.
Control your room temperature. Maintain a comfortable temperature in the bedroom. Extreme temperatures may disrupt sleep or prevent you from falling asleep.
See a doctor if your sleeping problem continues. If you have trouble falling asleep night after night, or if you always feel tired the next day, then you may have a sleep disorder and should see a physician. Your primary care physician may be able to help you; if not, you can probably find a sleep specialist at a major hospital near you.
Most sleep disorders can be treated effectively, so you can finally get the full night's sleep you need.
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