Most people feel tired during the day from time to time but are able to keep themselves awake.
Those people with narcolepsy, however, can suddenly go from being fully awake to sound asleep in the blink of an eye even whilst they are eating, walking, or talking. Attacks of unexpected sleep Narcolepsy is characterised by attacks of sleep at irregular and unexpected times. These attacks are sudden and uncontrollable and may occur in the middle of a conversation or whilst eating a meal. One minute someone is wide-awake, the next they are fast asleep. Sleep attacks may last only minutes or may last many hours, happening just once a day or throughout the day.