Chronic sleep deprivation is common in modern society and may result from a variety of factors, including work demands, social and family responsibilities, medical conditions, and sleep disorders. As sleep debt accumulates, individuals may experience reduced performance, increased risk for accidents and death, and detrimental effects on both psychological and physical health.
Sleep has two dimensions: duration (quantity) and depth (quality). When individuals fail to obtain adequate duration or quality of sleep, daytime alertness and function suffer. In response to sleep deprivation, sleep is often both longer and deeper. In many cases, however, sleep intensity can change without major changes in sleep duration. Sleep duration alone is therefore not a good indicator of how much sleep is needed to feel refreshed in the morning and function properly.
The definition, epidemiology, causes, and consequences of sleep deprivation are reviewed here. Insomnia, which is distinct from sleep deprivation, is reviewed separately. (see "Overview of insomnia" and "Clinical features and diagnosis of insomnia").
Sleep deprivation exists when sleep is insufficient to support adequate alertness, performance, and health, either because of reduced total sleep time (decreased quantity) or fragmentation of sleep by brief arousals (decreased quality).
Acute sleep deprivation refers to no sleep or a reduction in the usual total sleep time, usually lasting one or two days. Chronic sleep deprivation (also called sleep restriction) exists when an individual routinely sleeps less than the amount required for optimal functioning.