A sleep disorder is a physical and psychological condition or disturbance of sleep and wakefulness caused by abnormalities that occur during sleep or by abnormalities of specific sleep mechanisms. Although the sleep disorder exists during sleep, recognizable symptoms manifest themselves during the day. Accurate diagnosis requires a polysomnogram, widely known as a "sleep test."
It is estimated that some 40 million Americans suffer from chronic, long-term sleep disorders. Another 20 to 30 million Americans suffer from some kind of sleep disorder on an irregular basis. The annual costs in productivity, health care, and safety have been estimated in the billions of dollars.
There are some 84 defined sleep disorders, according to the 1997 edition of the International Classification of Sleep Disorders (ICSD). This Sleep Disorders section currently offers information on several of the more common sleep disorders and groups of disorders. This information base will be continually expanding.
For basic information on sleep, and how to work with your doctor to determine if you do have a sleep disorder, see our Sleep Basics section.