Chronic Sleep Loss Damages the Body

Chronic partial sleep loss of even two to three hours per night was found to have detrimental effects on the body, leading to impairments in cognitive performance, as well as cardiovascular, immune, and endocrine functions, according to a new study.

Researchers at Northwestern University (Chicago, IL, USA) kept animals awake for 20 hours per day followed by a four-hour sleep opportunity, over five consecutive days. The team monitored brain wave and muscle activity patterns in order to precisely quantify sleep-wake patterns. After the first day of sleep loss the animals compensated for it by increasing their intensity (depth) of sleep, indicative of a homeostatic response. However, on the subsequent days of sleep loss, the animals failed to generate this compensatory response and did not sleep any more deeply or any longer than they did under non-sleep deprived conditions. At the end of the study, the animals were given three full days to sleep as much as they wanted, but they recovered virtually none of the sleep that was lost during the five-day sleep deprivation period.

The findings suggest that this change in the sleep regulatory system is reflective of an allostatic response. In the short term, allostatic responses are adaptive, but when sustained on a chronic basis, such as in this study, an allostatic load will develop and lead to negative health outcomes. The allostatic load resulting from the accumulating sleep debt loops back to the sleep regulatory system itself and alters it. The researchers suggest that animals may undergo a change in their need for sleep, or in their sleep homeostat, in situations where normal sleep time is prohibited or where sleep could be detrimental for survival. The study was published in the June 19, 2007, issue of the Proceedings of the National Academy of Sciences (PNAS).

Even though animals and humans may be able to adapt their sleep system to deal with repeated sleep restriction conditions, there could be negative consequences when this pattern is maintained over a long period of time, said lead author Fred W. Turek, a professor of neurobiology and physiology and director of Northwestern's Center for Sleep and Circadian Biology. This brings us back to the idea that repeated partial sleep restriction in humans has been linked to metabolic dysfunction and cardiovascular disease.


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