Narcolepsy is a rare but not-so-rare neurological disorder that affects around one in 2000 people. It is thought to be the result of an autoimmune attack that nixes twin spots in the hypothalamus, each about the size of a garden pea.
This brain damage, for there is no other way of putting it, upsets the neural circuitry responsible for maintaining either wakefulness or sleep. As a consequence, people with narcolepsy suffer from excessive sleepiness during the daytime, excessive wakefulness at night and spend a whole lot of time somewhere in between.
Subjectively narcolepsy is a complete bummer. Objectively it is without question the most fascinating sleep disorder and the starting point for an exciting new book I am writing on sleep and sleep disorders.
I am a trustee of Narcolepsy UK.