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Sleep disorders are disturbances that affect the ability to fall asleep, stay asleep, or stay awake or that cause abnormal behaviors during sleep, such as night terrors or sleepwalking.

• Sleep can be disturbed by many factors, including irregular bed times, activities before bed, stress, diet, disorders, and drugs.
• Lack of sleep makes people feel sleepy, tired, and irritable during the day and interferes with functioning.
• Less often, a sleep disorder makes people unable to resist falling asleep during the day.
• A detailed description of the problem, sometimes with information from a sleep log, usually indicates the diagnosis, but sometimes testing in a sleep laboratory is needed.

Sleep is necessary for survival and good health, but why sleep is needed and exactly how it benefits people are not fully understood. Individual requirements for sleep vary widely: usually from 6 to 10 hours every day. Most people sleep at night. However, many people must sleep during the day to accommodate work schedules—a situation that can lead to sleep disorders.

Did You Know... No one knows exactly why people need to sleep.

How long people sleep and how rested they feel after waking can be influenced by many factors, including level of excitement or emotional distress, age, diet, and use of drugs. For example, some drugs make people sleepy, and others make sleeping difficult. Some food components or additives, such as caffeine, strong spices, and monosodium glutamate (MSG), may disturb sleep. Older people tend to fall asleep earlier, to awaken earlier, and to be less tolerant of changes in sleep habits (for example, they may be more prone to jet lag and problems related to shift work). Compared with younger adults and children, older people are more easily aroused from sleep and awaken more often during the night. Whether older people need less sleep is unclear. They probably need as much sleep as younger people but do not sleep as well as they used to, leading to daytime sleepiness and napping. Napping during the day may help compensate for poor sleep during the night, but it may also contribute to the problem.

Spotlight on Aging Up to half of older people say that they do not sleep as well as they would like. Although causes may be the same as for younger people, age-related changes may also contribute. As people age, they may participating in fewer activities and become less physically active, making falling sleep harder. If people have to move into a relative's home or a nursing home, they may have no control over such things as temperature and noise levels. The resulting discomfort can make sleeping more difficult. If people go out less and spend less time outdoors, their exposure to sunlight is decreased. Exposure of the eyes to sunlight is necessary for the body to produce melatonin, a hormone that helps promote sleep. Also, the aging body produces less melatonin and growth hormone (which promotes deep sleep). Usually, older people tend to fall asleep and wake up earlier. They may take longer to get to sleep. They also spend less time in deep sleep (which helps the body recover from daytime activities). Once asleep, they wake up more often and more easily. As a result, they feel less refreshed when they wake up, even though they may have spent a long time in bed. Older people are more likely to have medical and emotional disorders that can interfere with sleep. Disorders interfere with sleep in several ways: By causing pain (as occurs in arthritis) By making breathing difficult (as occurs in heart or lung disorders) By making people have to urinate more often, waking them up frequently during the night (as occurs in benign prostatic hyperplasia, diabetes, or heart failure) Depression, which is common among older people, also interferes with sleep. Older people are more likely to take drugs that affect sleep. Some (such as diuretics for heart failure) increase the need to urinate and thus interrupt sleep. Other drugs make people sleepy during the day or stimulate them. Either way, sleeping at night may be harder. Older people tend to take naps because they do not sleep well during the night. Napping may be more likely because the aging body is less able to regulate blood pressure as needed. For example, after a big meal, blood pressure decreases, and the body needs to pump relatively more blood to the head. The aging body is less able to make this adjustment. As a result, older people feel sleepy. Generally, older people need as much sleep as they did when they were young and should not accept poor sleep as part of aging. They can take measures to improve sleep. Staying active, spending time outside, avoiding foods and beverages (such as those that contain caffeine) that can interfere with sleep, going to bed at regular times, and making sure their bedroom is conducive to sleep can help.

All sleep is not the same. There are two main types of sleep: rapid eye movement (REM) sleep and nonrapid eye movement (non-REM) sleep, which has four stages. People normally cycle through the four stages of non-REM sleep, usually followed by a brief interval of REM sleep, every 90 minutes or 5 or 6 times every night.

• Non-REM sleep: Non-REM sleep accounts for about 75 to 80% of total sleep time in adults. Sleep progresses from stage 1 (the lightest level, when the sleeper can be awakened easily) to stage 4 (the deepest level, when the sleeper can be awakened with greater difficulty). In stage 4, blood pressure is at its lowest, and heart and breathing rates are at their slowest.
• REM sleep: Electrical activity in the brain is unusually high, somewhat resembling that during wakefulness. The eyes move rapidly, and muscles are paralyzed so that voluntary movement is impossible. However, some muscles may twitch involuntarily. The rate and depth of breathing increase.

The most vivid dreaming occurs during REM sleep. Most talking during sleep, night terrors, and sleepwalking occur during stages 3 and 4.

Stages of the Sleep Cycle People normally cycle through distinct stages of sleep 4 or 5 times during the night. Relatively little time is spent in stage 1 (shallow) sleep. The greatest time is spent in stage 2 sleep. Deep sleep (stages 3 and 4) occurs mostly during the first half of the night, whereas more time is spent in rapid eye movement (REM) sleep as the night progresses. Brief awakenings occur throughout the night, most of which the sleeper is typically unaware of.

Symptoms

The most common symptoms are insomnia and excessive sleepiness during the day. People with insomnia have difficulty falling and staying asleep and wake up feeling unrefreshed. People with excessive daytime sleepiness tend to fall asleep during normal waking hours.

Some sleep disorders involve involuntary movements of the limbs or other unusual behaviors (such as nightmares) during sleep.

Other symptoms may include problems with memory, coordination, and emotions. People may perform less well in school or at their jobs. The risk of having a motor vehicle accident or developing a heart disorder is increased.

Diagnosis

Usually, sleep disorders can be diagnosed based on the medical history, including a description of the current problem, and results of a physical examination. Doctors ask for a detailed description of the problem and may ask people to keep a sleep log. In it, people record the following:

• When they go to sleep
• When they awaken in the morning
• How many times they wake up during the night
• How long they stay awake each time they wake up
• What they do before going to bed
• How they feel the next day (for example, whether they feel drowsy)
• Whether they take any naps, at what time, and how long they last

Science Wakes Up to Sleep Disorders People with all types of sleep disorders are sent to sleep disorder specialists for evaluation, diagnosis, and treatment. Some people require testing in a sleep laboratory. The following symptoms may prompt such a referral: Excessive daytime sleepiness Long-standing (chronic) insomnia Dependence on sleep aids Pauses in breathing during sleep Severe snoring or choking during sleep Nightmares Sleepwalking, talking during sleep, or violent movements during sleep Twitching of the legs or arms during sleep An irresistible urge to move the legs or arms just before or during sleep An initial evaluation by a sleep disorders specialist may include the following: A sleep history, often including a sleep log A general medical history A physical examination Following the initial evaluation, further testing may be obtained such as blood tests and sleep laboratory testing. Sleep laboratory testing includes overnight polysomnography and a multiple sleep latency test. In overnight polysomnography, people spend the night in a sleep laboratory with electrodes pasted to their scalp, facial area, and chin. With this information, sleep stages can be characterized. Electrodes are also attached to other areas of the body to record heart rate and muscle activity. Other bodily functions, such as breathing pattern, are also monitored and recorded. Polysomnography is used to detect breathing disorders, epilepsy, and unusual movements and behaviors during sleep (periodic limb movement disorder and parasomnias). In a multiple sleep latency test, people spend the day in a sleep laboratory, taking four or five naps at 2-hour intervals. This test is used to detect daytime sleepiness and to diagnose narcolepsy.

When the diagnosis is uncertain or when doctors suspect certain types of sleep disorders, evaluation in a sleep laboratory may be recommended. The evaluation consists of polysomnography and observation and sometimes video recording of unusual movements during an entire night's sleep. Polysomnography includes the following:

• Electroencephalography (EEG), which records the brain's electrical activity (see Diagnosis of Brain, Spinal Cord, and Nerve Disorders: Electroencephalography.)
• Electrocardiography (ECG), which records heart rhythm and rate
• Recording and monitoring of breathing functions
• Electro-oculography, which records eye movement during REM sleep
• Electromyography, which records muscle activity of the facial area and legs
• Oximetry, which records oxygen levels in the blood with a painless ear clip or finger clip

Last full review/revision March 2008 by Karl Doghramji, MD