Sleep Disorders

A sleep disorder is just what its name implies: something abnormal about the way a person is sleeping. It might be that he or she cannot get enough sleep, as is the case in insomnia (in-SOM-nee-a). In hypersomnia (HY-per-SOM-nee-a), the individual sleeps too much. In still other kinds of sleep disorders, events such as night terrors may interfere with sleep.


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Why Are Sleep Disorders Important?

When people do not get a normal refreshing sleep, they are not at their best. They may be impatient or careless, or they may show poor judgment in the things they do. They also may be irritable with family and friends. Sleeplessness can cause serious accidents, as when someone "nods off" while driving a car or operating machinery.

An estimated 30 million to 40 million Americans have serious sleep problems that can be damaging to their health. In the case of insomnia alone, estimates of the cost in terms of lost productivity reach many billions of dollars.

In order to understand sleep disorders, it is necessary to understand something about sleep itself and the wide range of normal variations in the way people sleep.

What Is Normal Sleep?

On average, about one-third of a person's life is spent sleeping. However, the amount and timing of sleep vary considerably in different people, based on their age and lifestyle. Newborn infants may sleep up to 20 hours a day. Young and middle-aged adults sleep about 8 hours on average. Elderly people tend to get less sleep at night but may take naps during the day.

Researchers use electroencephalograms (EEGs) and positron emission tomography (PET scans) to study sleep disorders. These PET scans show various stages of sleep and wakefulness. When awake (left), the brain shows active areas in red and yellow, with inactive areas in blue. During normal sleep (center), the brain is less active, and most areas show as blue. During deep sleep and non-REM sleep (right), the brain is active but not as active as during REM sleep (not shown) or wakefulness. © Hank Morgan, Science Source/Photo Researchers, Inc.
Researchers use electroencephalograms (EEGs) and positron emission tomography (PET scans) to study sleep disorders. These PET scans show various stages of sleep and wakefulness. When awake (left), the brain shows active areas in red and yellow, with inactive areas in blue. During normal sleep (center), the brain is less active, and most areas show as blue. During deep sleep and non-REM sleep (right), the brain is active but not as active as during REM sleep (not shown) or wakefulness.
© Hank Morgan, Science Source/Photo Researchers, Inc.

The timing of sleep often is determined by such factors as work schedules, but it is affected by lifestyle as well. Some individuals seem to be morning people, or "early birds," by nature, whereas others are "night owls," preferring to stay up late.

What Are the Types and the Stages of Sleep?

Scientists at sleep laboratories have discovered that there are two distinct types of sleep. One is called rapid eye movement, or REM, sleep, because the eyes can be seen moving rapidly beneath the closed eyelids. Dreaming takes place during REM sleep, and the brain waves of someone in REM sleep look much like those of someone who is awake when the waves are measured on an electroencephalogram (ee-LEK-tro-en-SEF-a-lo-gram), or EEG.

The other type is non-REM sleep. It consists of four stages in which the brain waves progressively become deeper and slower but then speed up again until the REM stage occurs. This cycle normally is repeated with some variation at approximately 90-minute intervals, with REM sleep usually taking up about 25 percent of the total.

Studies conducted at sleep laboratories have contributed greatly to the diagnosis and treatment of sleep problems. The following are some of the more common sleep disorders.


Insomnia is a general term for trouble sleeping ("somnia" comes from the Latin somnus, which means sleep). The disorder is very common, as can be inferred from the fact that sleeping pills are among the most widely used of all medications. People with insomnia may have difficulty falling asleep, or they may wake up too early in the morning. Some wake up frequently during the night and then find it hard to go back to sleep.

Because people need different amounts of sleep, insomnia is not defined by hours of sleep. Insomnia is classified according to how long it lasts. Transient, or short-term, insomnia lasts from one night to a few weeks. Causes may include stress, excitement, or a change in surroundings. Chronic * insomnia, which occurs almost every night for a month or more, is a complex disorder with multiple causes.

Sleep apnea

A person with sleep apnea (AP-nee-a) stops breathing intermittently while asleep, for periods of about 10 seconds or more. The most common and severe type is obstructive sleep apnea. In this disorder, the muscles at the back of the throat relax and sag during sleep, until they obstruct the airway. The pressure to breathe builds up until the sleeper gasps for air. These episodes may occur hundreds of times a night and are accompanied by wakings so brief that they usually are not remembered. People with sleep apnea typically complain of being very tired during the day. Severe sleep apnea can induce high blood pressure and increase the risk of stroke * , heart attack, and even heart failure.

* chronic (KRON-ik) means continuing for a long period of time.

* stroke is a blocked or ruptured blood vessel within the brain, which deprives some brain cells of oxygen and thereby kills or damages these cells. Also called apoplexy (AP-o-plek-see).


Narcolepsy (NAR-ko-lep-see), like sleep apnea, involves excessive daytime sleepiness. In narcolepsy, however, the person cannot resist falling asleep. Sleep attacks crop up at odd and inappropriate times, such as while eating or talking to someone. Another symptom is cataplexy (KAT-a-plek-see), a sudden attack of muscular weakness that can make the person go limp and fall. Some people with narcolepsy also experience frightening hallucinations * or sleep paralysis * , an inability to move or speak, while falling asleep or waking up. Research has shown that during a sleep attack, the REM stage of sleep intrudes suddenly into the waking state. Narcolepsy is a lifelong condition of unknown cause. Narcoplesy does run in families. Sometimes socially embarrassing or inconvenient, this disorder can also be severely disabling and cause injury.


People with hypersomnia may sleep excessively during the day or longer than normal at night. Drowsiness or sleep periods last longer than with narcolepsy. Psychological depression * often is the main cause. A rare type of hypersomnia called Kleine-Levin syndrome * is characterized by periods of overeating as well as oversleeping. It occurs most often in teenage boys.

Jet lag

When an air traveler crosses several time zones, jet lag occurs. The body's internal "clock" then is desynchronized (or out of sync) with local time. Temporarily, people with jet lag may find it difficult to stay awake during the day or be unable to sleep at night.

* hallucinations (ha-loo-si-NAY-shunz) are sensory perceptions without a cause in the outside world.

* paralysis (pa-RAL-i-sis) is the loss or impairment of the ability to move some part of the body.

* depression (de-PRESH-un) is a mental state characterized by feelings of sadness, despair, and discouragement.

* syndrome means a group or pattern of symptoms that occur together.

The Poets on Sleep
and Sleep Disorders

William Shakespeare expressed in poetic terms the value and purpose of sleep when he wrote, "Sleep that knits up the ravell'd sleave of care,/The death of each day's life, sore labour's bath,/Balm of hurt minds, great nature's second course,/Chief nourisher in life's feast" (Macbeth, Act II, Scene 2).

In modern times, the humorous poet Ogden Nash, who delighted in creating whimsical rhymes, showed familiarity with sleep problems in this verse: "Sleep is perverse as human nature,/Sleep is as perverse as a legislature,/Sleep is as forward as hives or goiters,/And where it is least desired, it loiters" ( The Face Is Familiar. Read This Vibrant Expose).


Almost everyone has nightmares occasionally. These unpleasant, vivid dreams occur during REM sleep, usually in the middle or late hours of the night. Upon awakening, the dreamer often remembers the nightmare clearly and may feel anxious. Nightmares are especially common in young children. In adults, they may be a side effect of certain drugs or of traumatic events, such as accidents.

Night terrors and sleepwalking

A night terror is quite different from a nightmare. It occurs in children during deep non-REM sleep, usually an hour or two after going to bed. During an episode, they may sit up in bed shrieking and thrashing about with their eyes wide open. Typically, the next day they remember nothing of the event. Night terrors occur chiefly in preschool children. Although frightening, they generally are harmless and are soon outgrown.

Sleepwalking also occurs during non-REM sleep. It was once believed to be the acting out of dreams, but this is not the case. It takes place most commonly in children. The sleepwalker wanders about aimlessly, appearing dazed and uncoordinated, and remembers nothing of the episode afterward.

How Do Doctors Diagnose and Treat Sleep Disorders?

Most sleep disorders can be treated successfully if diagnosed properly. Anyone who sleeps poorly for more than a month or has daytime sleepiness that interferes with normal activities may wish to consult a doctor or be referred to a specialist in sleep disorders.

At a sleep clinic, patients first are asked questions about their medical history and sleep history. A polysomnogram (pol-ee-SOM-no-gram) is sometimes used to measure brain waves, muscle activity, breathing, and other body functions during sleep.

Many sleep disorders, such as jet lag, short-term insomnia, and most nightmares, do not need treatment. Some others, such as night terrors, are outgrown.

Chronic insomnia often is treated successfully with behavior therapy, which involves various relaxation techniques and reconditioning to change poor sleeping habits. Sleeping pills may be used temporarily, but their long-term use is controversial because of unwanted side effects.

Obstructive sleep apnea often is treated with dental appliances or a device known as CPAP (continuous positive airway pressure) to keep the airway open. Operations sometimes are performed to treat severe obstructive sleep apnea.

Hypersomnia due to depression is often helped by psychotherapy * . There is no cure for narcolepsy, but medications can help control or ease symptoms.


Some over-the-counter sleep aids contain melatonin (mel-a-TO-nin). Melatonin is a hormone secreted during darkness by the pineal (PIN-e-al) gland, a small structure located over the brain stem * .

Melatonin appears to be part of the system that regulates our sleep-wake cycles. Some research studies have shown that a small dose of melatonin at night helps make falling asleep easier, and that melatonin may be beneficial to travelers who have jet lag.

Melatonin is available for sale without a prescription, but the U.S. Food and Drug Administration does not regulate its production or sale. Studies still are being conducted to determine whether melatonin is safe for use.

* brain stem is the part of the brain that connects to the spinal cord. The brain stem controls the basic functions of life, such as breathing and blood pressure.

* psychotherapy (SY-ko-THER-a-pee) is the treatment of mental and behavioral disorders by support and insight to encourage healthy behavior patterns and personality growth.

Guidelines for Prevention

Most sleep disorders can be prevented or minimized by making a few changes in one's lifestyle. The following are some simple guidelines:

  • Avoid excessive amounts of caffeine or alcoholic beverages, especially soon before bedtime. The same goes for smoking cigarettes. Avoid frequently disrupted sleep-wake schedules.
  • Avoid excessive napping in the afternoon or evening.
  • Exercise regularly, but not just before retiring.

Did You Know?

  • Our eyes move when we dream much as they do when we are awake.
  • A person who lived to be 70 would spend about 6 years dreaming.
  • In one sleep disorder, apnea, people can stop breathing hundreds of times each night.
  • In another, narcolepsy, someone can fall asleep while having a conversation.
  • Night terrors are different from nightmares.
  • People who sleepwalk are not acting out their dreams.

See also
Depressive Disorders
Jet Lag
Sleep Apnea
Sudden Infant Death Syndrome (SIDS)



Remmes, Ann, and Roxanne Nelson. If You Think You Have a Sleep Disorder. New York: Dell Publishing Co., 1998.


The National Heart, Lung, and Blood Institute (NHLBI), part of the U.S. National Institutes of Health (NIH), posts information about insomnia on its website.

The National Institute of Neurological Disorders and Stroke (NINDS), part of the U.S. National Institutes of Health (NIH), posts information about sleeping disorders on its website.

The National Sleep Foundation posts a fact sheet, The Nature of Sleep, on its website.

Center for Narcolepsy Research (CNR), College of Nursing, The University of Illinois at Chicago, 845 South Damen Avenue, Room 215, Chicago, IL 60612-7350. CNR posts information about narcolepsy on its website.
Telephone 312-996-5176

The Nemours Foundation posts a fact sheet, Coping with Night Terrors, on its website.

Also read article about Sleep Disorders from Wikipedia

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