Narcolepsy is a neurological disorder that affects the control of sleep and wakefulness. People with narcolepsy experience excessive daytime sleepiness and intermittent, uncontrollable episodes of falling asleep during the daytime. These sudden sleep attacks may occur during any type of activity at any time of the day. Some patients with narcolepsy may also experience involuntary muscle weakness called cataplexy, which is usually brought about by laughter or anger.
In a typical sleep cycle, we initially enter the early stages of sleep followed by deeper sleep stages and ultimately (after about 90 minutes) rapid eye movement (REM) sleep. For people suffering from narcolepsy, REM sleep occurs almost immediately in the sleep cycle, as well as periodically during the waking hours. It is in REM sleep that we can experience dreams and muscle paralysis -- which explains some of the symptoms of narcolepsy.
Narcolepsy usually begins between the ages of 15 and 25, but it can become apparent at any age. In many cases, narcolepsy is undiagnosed and, therefore, untreated. Narcolepsy is a chronic condition and there is no cure, but wake-promoting medications may be very beneficial.