Sleep is absolutely essential for normal, healthy function. Scientists and medical professionals do not fully understand this complicated, necessary, physiological phenomenon. According to the National Institute of Neurological Disorders and Stroke, about 40 million people in the United States suffer from chronic long-term sleep disorders each year and an additional 20 million people suffer occasional sleep problems.
There are more than 70 different sleep disorders that are generally classified into one of three categories:
In most cases, sleep disorders can be easily managed once they are properly diagnosed. Insomnia is the most common sleep disorder. It occurs more often in women and in the elderly.
The amount of sleep that a person needs to function normally depends on several factors (e.g., age). Infants sleep most of the day (about 16 hours); teenagers usually need about 9 hours a day; and adults need an average of 7 to 8 hours a day. Although elderly adults require about as much sleep as young adults, they usually sleep for shorter periods and spend less time in deep stages of sleep. About 50% of adults over the age of 65 have some type of sleep disorder, although it is not clear whether this is a normal part of aging or a result of medications that older people commonly use.
Falling asleep and waking up are controlled by various chemical changes in the brain and in the blood. Foods and medicines that alter the balance of these chemicals also affect how well we sleep. Caffeine, for example, can cause insomnia (lack of sleep). Antidepressants can cause a loss of REM (rapid eye movement) sleep, as can smoking and alcohol. Smoking and alcohol also can result in a loss of deep sleep. Both REM and deep sleep are essential parts of the normal sleep cycle.
What is Sleep?
Sleep is a dynamic process during which the brain is very active. There are recognized stages of sleep, each of which is characterized by a different type of brain wave activity.
Stages of Sleep
There are five stages of sleep that cycle over and over again during a single night's rest: stages 1, 2, 3, 4 and REM (rapid eye movement). Stages 1 through 4 are also known as non-rapid eye movement sleep (NREM). About 50% of sleep time is spent in stage 2 and about 20% is spent in REM (normally more than 2 hours a night in adults). A complete sleep cycle, from the beginning of stage 1 to the end of REM, usually takes about an hour and a half.
Stage 1 is light sleep during which the muscles begin to relax and a person can be easily awakened. During stage 2, brain activity slows down and eye movement stops. Stages 3 and 4 comprise deep sleep, during which all eye and muscle movement ceases. It can be difficult to wake a person during deep sleep. Stage 3 is characterized by very slow brain waves (delta waves), interspersed with small, quick waves. In stage 4, the brain waves are all delta waves.
It is during deep sleep that some people sleepwalk and children may experience bedwetting. It is during REM sleep that dreams occur. The muscles of the body stiffen, the eyes move, the heart rate increases, breathing becomes more rapid and irregular, and the blood pressure rises.
Why Does the Body Need Sleep?
It is not clear exactly why the body requires sleep, although inadequate sleep can have severe detrimental effects on health. Studies have shown that sleep is essential for normal immune system function and to maintain the ability to fight disease and sickness. Sleep also is essential for normal nervous system function and the ability to function both physically and mentally. In addition, sleep is essential for learning and for normal, healthy cell growth.
Movement Disorders/ Stroke/ Sleep Disorders/ Multiple Sclerosis
Headache/ Memory/ Restless Legs/ PeriodicLeg Movements of Sleep