A persistent inability to sleep problems, remain asleep through the night, or feel refreshed by sleep is known as insomnia. At least 40 million Americans each year suffer from chronic, long-term sleep disorders each year, and an additional 20 million experience occasional sleeping problems. These disorders and the resulting sleep deprivation interfere with work, driving, and social activities. They also account for an estimated $16 billion in medical costs each year, while the indirect costs due to lost productivity and other factors are probably much greater. Doctors have described more than 70 sleep disorders, most of which can be managed effectively once they are correctly diagnosed. The most common sleep disorders include insomnia, sleep apnea, restless legs syndrome, and narcolepsy.

Almost everyone occasionally suffers from short-term insomnia. This problem can result from stress, jet lag, diet, or many other factors. Insomnia almost always affects job performance and well-being the next day. About 60 million Americans a year have insomnia frequently or for extended periods of time, which leads to even more serious sleep deficits. Insomnia tends to increase with age and affects about 40 percent of women and 30 percent of men. It is often the major disabling symptom of an underlying medical disorder.

Sleep apnea is a disorder that causes people to stop breathing for short periods during sleep. These periods are called apneas. They usually last between 10 and 30 seconds. In severe cases, apneas can happen many hundreds of times each night, disrupting the person's ability to get a good night's sleep. This makes the person less alert during the day, which can lead to accidents. People with untreated sleep apnea are up to seven times more likely to be involved in motor vehicle accidents. People with untreated sleep apnea also are more likely to develop high blood pressure. Sleep apnea usually happens when the breathing airway in your nose or throat becomes blocked partially or completely. It can be blocked by large tonsils, a large tongue or by too much tissue in the airway, which is more common in people who are overweight. When airway muscles relax during sleep, this extra tissue can block the breathing passages. This is called obstructive sleep apnea. Sleep apnea also can happen when the brain stem, the area of the brain that controls breathing, is damaged, for instance by an infection or stroke. This is called central sleep apnea. Studies show that sleep apnea affects approximately 9% of middle-aged men and 4% of middle-aged women.