Narcolepsy is a neurological sleep disorder that usually first appears between the ages of 10 and 30. It is a rare disorder, only affecting about 1 in 2,000 people. Someone with narcolepsy can suddenly feel uncontrollably sleepy during the day, a symptom referred to as excessive daytime sleepiness (EDS). These episodes can happen multiple times a day and at any time, even while driving or talking.
Another symptom of narcolepsy is an abnormal sleep pattern. Someone with a normal sleep pattern transitions from non-rapid eye movement (NREM) sleep to rapid eye movement (REM) sleep in about 90 minutes after falling asleep. However, someone with narcolepsy transitions to REM sleep after being asleep for only about 15 minutes. REM sleep is the stage of sleep when vivid dreaming may occur. The boundary between being awake and dreaming while asleep is so close in people with narcolepsy that they may experience sleep paralysis (an inability to move or speak) or dream-like hallucinations.
A person with narcolepsy may also experience episodes of cataplexy, which is a sudden loss of muscle tone. A severe case of cataplexy may cause someone to suddenly fall to the ground. Narcolepsy with cataplexy is referred to as type 1 narcolepsy, and narcolepsy without cataplexy is called type 2 narcolepsy.
Researchers have not yet found what exactly causes narcolepsy but have discovered that many people with type 1 narcolepsy have low hypocretin levels. Hypocretin is a neurotransmitter that keeps you awake. Someone with a low hypocretin level feels sleepy and has an abnormal pattern of REM sleep. Scientists are not sure what causes the loss of neurons in the brain that produce hypocretin but researchers have found evidence that this loss may be linked to certain genes.
Leaving narcolepsy untreated can be dangerous since the sleep episodes can happen during any activity, even walking or eating. Narcolepsy can also impact performance at work or school. There is no cure for narcolepsy but symptoms can be managed with medication and lifestyle changes.