© Ascend Media

xcessive daytime sleepiness (EDS) may not seem like a seri-ous medical problem until you consider the fact that the states of sleepiness and alertness are mutually exclusive. Thus, a sensation of sleepiness is always reflective of an inability to perform expected waking functions. Sleepiness is not the same as fatigue, which is characterized by a reduced capacity (cognitive or muscular) and is often accompanied by weariness. Lack of sleep makes one sleepy; lack of rest makes one fatigued. There is overlap. Sleep lacking in quality—passing a restless night, for example—can cause one to feel fatigued as well as sleepy, whereas simply not getting enough sleep tends to leave one sleepy. Causes of EDS can be medical, neurological, or psychiatric—or EDS can be a function of sleep habits, usually driven by economic pres-sures. Although everyone has had the experience of interrupted, spo-radic, or nonrefreshing sleep, it is when this becomes chronic tha