National Sleep Foundation

Chapter 1: Normal Sleep

Sleep Disorder Statistics

Sleep Disorder Statistics

Sleep disorders are among the most common medical complaints in our society. The 2005 Sleep in America Poll, conducted by the National Sleep Foundation1, indicated that 75% of adults surveyed reported having at least 1 symptom of a sleep problem a few nights a week or more (up from 62% in 1999, 69% in 2000, and 74% in 2002).71 Severe insomnia is the most commonly reported sleep problem in the United States and affects about 10% of all adults. Add to this the millions of adults with other sleep problems such as obstructive sleep apnea, disorders of excessive daytime somnolence, including narcolepsy, circadian rhythm disorders, and parasomnias, and you can see the necessity of treating sleep disorders competently.

Clearly, sleep is not just the absence of wakefulness but a complex, multidimensional state of existence. Sleep needs vary between individuals and within individuals throughout normal aging, but the purpose and function of sleep is not yet fully understood. The sleep-wake cycle is regulated by both homeostatic and circadian processes. Sleep influences all major physiologic systems including the immune system, the musculoskeletal system, the endocrine system, and thermoregulation. Partial or total lack of sleep, either acute or chronic, can drastically change an individual’s thinking and behavior, and negatively impact physical, mental, and emotional health.


  1. National Sleep Foundation (NSF). Sleep in America poll. 2005. Available at: [Accessed June 21, 2006].