Definition of EDS (Excessive Daytime Sleepiness)

Reviewed on 10/21/2021

EDS (excessive daytime sleepiness) is a neurological disorder marked by a sudden recurrent uncontrollable compulsion to sleep. It is also known as narcolepsy. It is often associated with cataplexy (a sudden loss of muscle tone and paralysis of voluntary muscles associated with a strong emotion), sleep paralysis (immobility of the body that occurs in the transition from sleep to wakefulness), what are called hypnagogic hallucinations (pre-sleep dreams), and automatic behaviors (such as doing something "automatically" and not remembering afterward how one did it).

About 125,000 Americans are estimated to have narcolepsy. It strikes males and females and all races. Symptoms most commonly appear in a person's teens and early 20s. The disease can vary in severity. Some people with it have mild sleepiness or rare cataplexy (less than one episode per week). Other people may have moderate sleepiness or infrequent cataplexy (less than one episode a day). Still other people with narcolepsy may experience severe sleepiness or have severe cataplexy (with one or more episodes of cataplexy per day).

The cause(s) of narcolepsy are unknown. It is not a fatal disorder in itself but it can lead to fatalities. For example, a narcoleptic may fall asleep while driving.

Narcolepsy is usually treated with a medication to improve alertness and an antidepressant that helps control cataplexy.

Other names for narcolepsy include hypnolepsy, sleeping disease, paroxysmal sleep, and Gelineau syndrome.


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Jameson, J. Larry, et al. Harrison's Principles of Internal Medicine, 20th Ed. New York: McGraw-Hill Education, 2018.

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