Sleep Apnea, feeling tired sometimes, but roughly 20 percent of the population can be classified as having Excessive Sleepiness (sometimes referred to as Excessive Daytime Sleepiness).

Excessive sleepiness is the leading complaint of patients who visit sleep clinics. People who have excessive sleepiness feel drowsy and sluggish most days, and these symptoms often interfere with work, school, activities, or relationships. Although patients with this condition often complain of "fatigue," excessive sleepiness is different from fatigue, which is characterized by low energy and the need to rest (not necessarily sleep). Excessive sleepiness is also different from depression, in which a person may have a reduced desire to do normal activities, even the ones they used to enjoy