Narcolepsy is a chronic neurological sleep disorder, characterized by excessive day time sleepness in which a person experiences extreme fatigue and possible falls asleep at inappropriate time. It affects part of the brain that regulates when to be awake and when to be asleep. When a person with narcolepsy goes to bed they generally experience rapid eye movement. Narcoleptic episodes can occur at any time.

It affects both men and women. It is seen more common at the age of 15- 25 and also at an older age. It is seen all over the world but more in United States (25 per 1,00,000) and Japan (1 per 600).