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9 Most Common Sleep Disorders

Narcolepsy can be dangerous -- especially if the person falls asleep behind the wheel.
Narcolepsy can be dangerous -- especially if the person falls asleep behind the wheel.
Adam Gault/Digital Vision/Getty Images

What is it? Narcolepsy is characterized by extreme, overwhelming sleepiness during the day. It is caused by a dysfunction of the brain mechanisms controlling sleep and waking. The person may suddenly fall asleep in midsentence, while at work, or behind the wheel of a car. Other symptoms of narcolepsy include the sudden loss of muscle tone while awake when surprised or upset (which can be severe enough to cause a collapse), and vivid hallucinations as the person is falling asleep, and sleep paralysis, a condition in which the body's normal paralysis of large muscles during REM sleep fails to end upon waking. Narcolepsy appears to run in families.

How common is it? Narcolepsy is rare, occurring in about 100,000 Americans. It may start in childhood but typically peaks in young adulthood.

What's the treatment? The symptoms of narcolepsy can be found in several other conditions, including obstructive sleep apnea, so accurate diagnosis is critical. Researchers now believe that narcolepsy is caused by the lack of receptors for the neurotransmitter hypocretin, which regulates the sleeping and waking states. Modafinil, which promotes alertness, has been shown to be effective in the treatment of narcolepsy. Behavioral changes that can help include avoiding caffeine nicotine and alcohol in the late afternoon or evening, regular exercise at least three hours before bedtime, and scheduling several short naps or one longer nap (20 to 40 minutes) each day.