National Sleep Foundation

Chapter 1: Normal Sleep

Abnormal Sleep & Sleep Disorders

Sleep disorders are among the most common medical complaints in our society. The National Sleep Foundation’s (NSF) 2005 Sleep in America Poll indicated that 75 percent of adults surveyed reported having at least one symptom of a sleep problem at least a few nights a week — an increase from 62 percent in 1999, 69 percent in 2000, and 74 percent in 20021.

Millions of Americans suffer from sleep problems, including:

  • Insomnia, the most common sleep complaint, involves trouble getting to sleep and/or staying asleep, and/or experiencing unrefreshing sleep. About 30-40 percent of adults report some insomnia symptoms in any given year; about 10-15 percent of adults say they have chronic insomnia.2
  • Obstructive sleep apnea (OSA) is most common form of sleep apnea. It occurs when the person’s airway collapses or is blocked, which causes shallow breathing (or pauses in breathing) and disrupts sleep. While most OSA is undiagnosed, it may affect as many as four million Americans.3
  • Excessive sleepiness disorder is persistent sleepiness (what is often referred to as “tiredness”), which interferes with a person’s productivity and quality of life. It can result from sleep deprivation, insomnia, narcolepsy (disabling sleepiness), or cataplexy (sudden muscular weakness). According to NSF’s 2008 Sleep in America poll, 36 percent of Americans have driven while drowsy or fallen asleep while driving; 29 percent have fallen asleep or become very sleepy at work; 20 percent have lost interest in sex due to sleepiness; and 14 percent have missed family events, work functions, and/or leisure activities in the past month due to excessive sleepiness.4
  • Circadian Rhythm Disorders all involve problems with an individual’s internal clock that disrupt his or her sleep patterns. Shift work disorder (SWD), is a form of Circadian Rhythm Disorder with serious medical and psychiatric consequences; it is predominantly experienced by those who work night shifts and early morning shifts5.  Shift workers are more likely to suffer from insomnia and excessive daytime sleepiness compared to those who work during the day (61% vs. 47%, and 30% vs. 18% respectively). Shift workers are also more likely to drive while fatigued and to fall asleep at the wheel.6
  • Parasomnia: refers to all of the abnormal activities that can happen while people sleep (other than sleep apnea), including sleep-related abnormal movements, behaviors, emotions, perceptions, and dreams that occur while falling asleep, sleeping, between sleep stages, or during arousal from sleep. They include eating disorders, sleepwalking, nightmares, sleep paralysis, REM sleep behavior disorder, and sleep aggression. Parasomnias affect about 10 percent of Americans and are more common in children due to their brain immaturity.7
  • Restless legs syndrome (RLS) is a neurological disorder that causes uncomfortable (and sometimes painful) tingling and tugging sensations in the legs. RLS symptoms usually intensify in the evening and at night, and can interfere with sleep. RLS is often undiagnosed or misdiagnosed; about 10 percent of American adults suffer from RLS.8



  1. National Sleep Foundation (NSF). Sleep in America poll. Arlington: NSF, 2005. Available at:
  2. National Sleep Foundation (NSF). Can’t Sleep? What to Know About Insomnia, Arlington: NSF, no date. Available at:
  3. Institute of Medicine (IOM) Committee on Sleep Medicine and Research, Colten HR and Altevogt BM (ed.), Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem, Washington, DC: National Academy of Sciences, 2006.
  4. National Sleep Foundation (NSF). Fatigue and Excessive Sleepiness, Arlington: NSF, no date. Available at:
  5. Guardiola-Lemaitre B, Quera-Salva MA, Melatonin and the regulation of sleep and circadian rhythms. In: Kryger MH, Roth T, Dement WC, eds. Principles and Practice of Sleep Medicine. 5th ed. Philadelphia: Elsevier Saunders; 2011:420-430.
  6. National Sleep Foundation, Shift Work and Sleep, Arlington: NSF, no date.
  7. Schenck C, Mahowald M. “A polysomnographically documented case of adult somnambulism with long-distance automobile driving with frequent nocturnal violence: parasomnia with continuing danger as a noninsane automatism,” Sleep. 1995;18:765-772.
  8. National Sleep Foundation (NSF). Restless Leg Syndrome, Arlington: NSF, no date. Available at: