Excessive sleepiness (ES) is a very common complaint that can significantly impair a person's ability to function. ES has a wide spectrum of presentation, ranging from mild sleepiness to unrecognized episodes of "microsleeps" and uncontrollable sleep attacks. Excessive sleepiness can occur due to a variety of reasons. Common etiologies include obstructive sleep apnea, narcolepsy, and sleep deprivation. Other causes include circadian rhythm disorders (eg, nightshift work), underlying medical disorders, and drug effects. Young adults often complain of ES but it is usually a result of poor sleep hygiene and sleep deprivation. The advent of highly technologic societies has placed an impetus on productivity and efficiency. This thrust has brought about longer workdays and 24-hour work shifts. The individuals in modern society are chronically sleep-deprived, resulting in excessive sleepiness that is transparently manifest in passive situations. At present, human error causes the majority of industrial and transportation accidents. The increased prevalence of motor vehicle and work-related accidents are in large part due to the effects of ES. This syndrome has been shown to significantly impair judgment, memory, and concentration. Excessive sleepiness must be evaluated promptly and thoroughly, because it may represent a significant underlying medical disorder and because the symptom itself can have catastrophic consequences. About Sleep Disorders According to the National Institutes of Health, more than 70 million Americans suffer from disorders of sleep and wakefulness. Of that, nearly 60 percent have a chronic disorder. Defined as a physiological condition that causes disruptive sleep patterns, sleep disorders inhibit an individual's mental and physical performance and can seriously affect one's health and quality of life. Sleep disorders can range in severity from snoring and restlessness, to gastro-esophageal reflux, to sleep apnea. The Importance of Diagnosis and Treatment Sleep disorders can seriously interfere with one's overall emotional or physical health, often leading to depression, reduced concentration, and impaired memory and judgment. The extreme fatigue caused by sleep disorders can inhibit an individual's job performance and social skills, as well as increase the risk of car- and work-related accidents. Lack of quality sleep also lowers the body's ability to resist and fight illnesses. As a result, the sleep-deprived person is often sick.