Overview of Sleep Disorders

Sleep is absolutely essential for normal, healthy function. Scientists and medical professionals still have much to learn about this complicated 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 experience occasional sleep problems.

There are more than 70 different sleep disorders, which are generally classified into one of three categories:

  • lack of sleep (e.g., insomnia),
  • disturbed sleep (e.g., obstructive sleep apnea), and
  • excessive sleep (e.g., narcolepsy).

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 in a normal manner depends on several factors, including 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 older adults require about as much sleep as younger 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 other factors, such as medications that are commonly used by older people.

Falling asleep and waking up are controlled by a number of chemical changes in the brain and the blood. Foods and medicines that alter the balance of these chemicals also can affect how well we sleep. For example, caffeine, which is found in coffee, tea, colas, and chocolate, can cause insomnia (lack of sleep) and antidepressants, alcohol, and smoking can cause a loss of REM (rapid eye movement) sleep. 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.

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.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 01 Jan 2000

Last Modified: 05 Dec 2011