|Classification and external resources|
|ICD-9||291.82, 292.85, 307.43-307.44, 327.1, 780.53-780.54|
Excessive daytime sleepiness (EDS) is characterized by persistent sleepiness, and often a general lack of energy, even after apparently adequate night time sleep. Sudden involuntary sleep onset, and microsleeps are common complications. EDS is a symptom of one of the two forms of the sleep disorder hypersomnia, the other being prolonged nighttime sleep.
Some persons with EDS, including those with narcolepsy, are compelled to nap repeatedly during the day; fighting off increasingly strong urges to sleep during inappropriate times such as while driving, while at work, during a meal, or in conversations. As the compulsion to sleep intensifies, the ability to competently complete tasks sharply diminishes, often mimicking the appearance of intoxication.
An adult who is compelled to nap repeatedly during the day may have excessive daytime sleepiness. However, it is important to distinguish between occasional daytime sleepiness and excessive daytime sleepiness, which is chronic.
A number of tools for screening for EDS have been developed. One is the Epworth Sleepiness Scale which grades the results of a questionnaire. The ESS generates a numerical score from zero (0) to 24 where a score of ten  or higher may indicate that the person should consult a specialist in sleep medicine for further evaluation. A self test is available at the the author's website.
Another tool is the Multiple Sleep Latency Test (MSLT), which has been used since the 1970s. It is used to measure the time it takes from the start of a daytime nap period to the first signs of sleep, called sleep latency. The test is based on the idea that the sleepier people are, the faster they will fall asleep.
EDS can be a symptom of a number of factors and disorders. Specialists in sleep medicine are trained to diagnose them. Some are:
EDS is often the manifestation of a disorder, and not a sign of a willful lack of effort. Without firm and knowledgeable counseling on the part of the physician, family members can easily fail to accept EDS as part of an illness.
EDS can affect the ability to function in family, social, occupational, or other settings. A proper diagnosis, and treatment, of the underlying cause can help mitigate such complications. It can be difficult to accept that EDS is beyond a person's control; the unaffected may see sleepiness as an insult, a rejection, or as evidence for lack of interest. During occasional unique and/or stimulating circumstances, a person with EDS can sometimes remain animated, awake and alert, for brief or extended periods of time; this lends credence to an observer's assertions that the alertness is simply a matter of self control and that EDS can be 'willed away'.
The medications modafinil (Provigil) and gamma-Hydroxybutyric acid (Xyrem) have been approved as a first-line treatment for EDS symptoms in the U.S., and have been proven extremely effective in the treatment of most symptoms. While there is declining usage of other drugs such as Ritalin, Dexedrine, Adderall, Desoxyn, and Cylert, these psychostimulants still provide additive assistance under varying circumstances. .