Adequate alertness is necessary for well-being and performance in modern society. Sleeping predisposes an individual to developing serious performance decrements in multiple areas of function, as well as to potentially life-threatening domestic, work-related, and driving accidents.
Narcolepsy is a chronic neurological disorder caused by the brain's inability to regulate sleep-wake cycles normally. At various times throughout the day, people with narcolepsy experience fleeting urges to sleep. If the urge becomes overwhelming, individuals will fall asleep for periods lasting from a few seconds to several minutes. In rare cases, some people may remain asleep for an hour or longer. In addition to excessive daytime sleepiness (EDS), three other major symptoms frequently characterize narcolepsy: cataplexy, or the sudden loss of voluntary muscle tone; vivid hallucinations during sleep onset or upon awakening; and brief episodes of total paralysis at the beginning or end of sleep. Narcolepsy is not definitively diagnosed in most patients until 10 to 15 years after the first symptoms appear.
The cause of narcolepsy remains unknown. It is likely that narcolepsy involves multiple factors interacting to cause neurological dysfunction and sleep disturbances.
Daytime sleepiness is defined as the inability to stay awake and alert during the major waking episodes of the day, resulting in unintended lapses into drowsiness or sleep.