Excessive sleepiness.

Sleepiness is a commonly experienced symptom affecting up to one-fifth of the population chronically. Sleepiness contributes to systemic health effects, and has been shown to contribute to mood disorders and cardiovascular risks. Sleepiness also presents a significant public health risk: it has been associated with major catastrophes, motor vehicle accidents, and medical errors by health care workers. This article reviews the implications of sleepiness on public health, the evaluation of sleepiness, disorders that result in sleepiness, and the management of these disorders.