Adult short sleepers habitually get 5-6 or fewer hours of sleep per 24 hours, without impairment in their daytime functioning.11 In children, short sleepers are those who get three hours or less than the norm for their age group.12 This condition may be linked to a genetic mutation (in other words, the condition is innate), which causes these individuals not to need to sleep longer.13
These individuals’ sleep is typically unbroken and, although short, is not a result of restricted sleep that has a negative impact on daytime functioning.14
Individuals who, for some reason, are not getting enough sleep are likely to suffer from Behaviorally Induced Insufficient Sleep Syndrome (ISS), also called “sleep deprivation.” They may take naps and/or sleep longer on weekends to try to “catch up” on missed sleep. For more information, see the section on Behaviorally-induced Insufficient Sleep Syndrome (ISS).
About four percent of adults in the United States report sleeping five or fewer hours per night. This number may be an over-estimate, however, as it includes people with behaviorally-induced ISS as well as those who suffer from insomnia or mania.15
Short sleepers have similar absolute amounts of slow-wave sleep (SWS) as do normal sleepers, while their amounts of stage 1, 2 and REM sleep are lower than normal.16 Because overall sleep time is short, the normal absolute amounts of SWS result in a higher percentage of SWS per night. Some studies suggest that, compared to long sleepers, short sleepers have an inherently different circadian rhythm (i.e., an internal clock that calls for a shorter-than-usual biological night).17
Short sleepers are considered to be psychologically normal and are typically described as efficient, not prone to worry, and possibly somewhat hypomanic.18,19 They may seek help from a sleep center because others worry that they are not getting enough sleep.
By definition, short sleepers have no impairment in daytime functioning; therefore, treatment is neither typical nor required.
11 Thorpy MJ, “Classifications of Sleep Disorders,” In Kryger M, Roth T, Dement W (ed.), Principles and Practice of Sleep Medicine (5th Edition), St. Louis: Elsevier Saunders, page 687.
12 Thorpy MJ, “Classifications of Sleep Disorders,” In Kryger M, Roth T, Dement W (ed.), Principles and Practice of Sleep Medicine (5th Edition), St. Louis: Elsevier Saunders, page 687.
13 He Y, Jones CR, Fujiki N, et al., “The Transcriptional Repressor DEC2 Regulates Sleep Length in Mammals,” Science 2009; 325(5942): 866–870. doi: 10.1126/science.1174443.
15 Kripke DF, Garfinkel L, Wingard DL, Klauber MR, Marler MR. Mortality associated with sleep duration and insomnia. Arch Gen Psychiatry. 2002;59:131-136.
16 American Academy of Sleep Medicine. International Classification of Sleep Disorders, 3rd edition: Diagnostic and Coding Manual. Darien, I: American Academy of Sleep Medicine; 2014.
18 Hartmann E, Baekeland F, Zwilling GR. Psychological differences between long and short sleepers. Arch Gen Psychiatry. 1972;26:463-468.