Daytime Sleepiness

woman leaning on top building rail during daytime

Undue Fatigue During the Day May Have Serious Underlying Causes

Approximately 1 of 5 American adults reports a level of daytime fatigue that interferes with normal function. The most common complaint of people who enter sleep clinics is excessive daytime sleepiness. (Johnson E. Sleep in America: 2000. Results from the National Sleep Foundation’s 2000 Omnibus sleep poll. Washington, DC: The National Sleep Foundation)

Adolescents, shift workers, and elderly persons report the highest levels of daytime sleepiness, but it is difficult to assess the true prevalence of the problem because symptoms of sleepiness are so subjective and there are no standardized approaches for its assessment and diagnosis.

Impact of Daytime Sleepiness

Regardless of difficulties in determining its overall prevalence, daytime sleepiness has a real impact on those whom it affects. Sleep problems have been associated with:

  • More than 100,000 motor vehicle accidents resulting in over 70,000 injuries and 1,500 deaths annually in the United States (National Sleep Foundation. State of the states report on drowsy driving. November 2007)
  • 52% of heavy truck accidents are fatigue-related, with the driver falling asleep in 18% of cases (NTSB. Factors that affect fatigue in heavy truck accidents safety study. Washington, DC: National Transportation Safety Board, 1995)
  • Low levels of academic performance, a higher incidence of school tardiness, and even lower graduation rates among adolescents (Pagel J, et al. Adolescent sleep disturbance and school performance: the confounding variable of socioeconomics. J Clin Sleep Med. 2007;3[1]:19-23)
  • Poor professional and job performance, notably among workers whose performance affects the wellbeing of others (e.g., physicians) (Chen I, et al. A survey of subjective sleepiness and consequences in attending physicians. Behav Sleep Med. 2008;6[1]:1-15)
  • Reduced cognitive function and energy levels, which interfere with acquiring and retaining employment, increase one’s risk of injury at work, and impair social function at all levels

Causes of Excessive Daytime Sleepiness

Sleep Deprivation

Sleep loss is the most prevalent cause of daytime sleepiness; symptoms can occur after only one night of sleep restriction. Those who are chronically sleep-deprived may not be aware of their cognitive and performance impairment.

Medications, Drugs, and Alcohol

Sedation is one of the most commonly reported side effects of prescription medications. Alcohol is the most widely-used non-prescription agent that has sedating effects. Some street drugs (e.g., marijuana) are sedating, and people who abuse methamphetamine, cocaine, or other stimulants can exhibit persistent daytime sleepiness following long periods of drug use.

Obstructive sleep apnea (OSA)

Excessive daytime sleepiness is the most common complaint among people who suffer from OSA, which is characterized by periodic episodes of airway obstruction, hypoxia, and repeated arousals during the night. Many individuals with OSA aren’t aware of the disruption in their sleep pattern. OSA is arguably the most dangerous disorder associated with daytime sleepiness due to its effects on other physiologic parameters (blood pressure, blood glucose, tissue oxygenation, etc.).


This disorder is caused by abnormalities in the control and timing of REM sleep, where REM intrudes into wakeful periods. Narcolepsy may be accompanied by cataplexy (the sudden and transient loss of muscle tone) and is often precipitated by emotions.

Other conditions

Stroke, head injury, depression and other psychiatric conditions, menstrual hypersomnia, and restless legs syndrome can lead to daytime sleepiness. Jet-lag and “shift-work disorder” could also be included in this category, although they may simply represent special cases of sleep deprivation caused by disruption in circadian rhythms.

Treatment for Daytime Sleepiness

Therapy for excessive daytime sleepiness is somewhat dependent on its underlying cause. Some causes – shift work or some medical conditions, for example – may not be altogether amenable to treatment.

Proper sleep hygiene is important for all individuals who suffer from daytime sleepiness. Sleep environment and pre-sleep activities (eating, exercise, entertainment, etc.) may require modification to allow proper sleep induction and maintenance.

The use of alcohol and recreational drugs must be moderated or discontinued by individuals whose sleep is disrupted by these agents.

OSA typically responds to the use of positive-pressure breathing devices during sleep. Since many sufferers of OSA are overweight, weight loss is a vital part of treatment.

Stimulant drugs can be used for some disorders (narcolepsy, shift-work disorder, etc.), and they can be added to treatments for other conditions (e.g., OSA) that don’t respond fully to traditional therapies. Modafinil (Provigil) is considered the first-line agent for most of these conditions. (Pagel J. Excessive daytime sleepiness. Am Fam Phys. 2009;79[5]:391-96)

Amphetamines and other stimulant drugs are used less commonly, mainly due to their potential for overuse and abuse, which would only exacerbate daytime sleepiness in the long run.

Excessive daytime sleepiness affects nearly 20% of Americans. In many, it adversely affects work performance and social function, and it is a leading cause of traffic- and work-related injuries. Excessive daytime sleepiness that lasts more than a day or so and that is not easily explained should be promptly evaluated.