University Wisconsin Madison Many a times we compromise on sleep to watch a favorite movie or get involved in some social activity, which is seemingly harmful for our health. Experts from the University of Wisconsin-Madison reveal that five nights of restricted sleep with four hours a night can affect the brain in the same way as noted after acute total sleep deprivation. The study supposedly highlights the detrimental effects of restricted sleep for both brain and body.

In the course of the investigation, researchers kept rats awake for 20 hours a day over five days and continuously recorded their brain waves with an EEG. Brain waves were examined when the rats were asleep as well as awake. Measurements taken with the help of the EEG reported slow wave activity (SWA) and intensity of sleep that follows a period of wakefulness. It was affirmed that SWA is the best marker of an individual’s need to sleep.

“Even relatively mild sleep restriction for several nights can affect an individual’s ability to perform cognitive tasks. For instance, recent studies in humans have shown that five days with only four hours of sleep/night result in cumulative deficits in vigilance and cognition, and these deficits do not fully recover after one night of sleep, even if 10 hours in bed are allowed. Sleep restriction can also increase resistance to insulin, leading to a risk of diabetes,” affirmedDr. Chiara Cirelli, associate professor of psychiatry at the School of Medicine and Public Health, who led the research.

After analyzing rat cumulative SWA measures, experts noted that sleep restriction produced intense recovery sleep following each wake cycle, with both longer and deeper sleep. With elevation in the ability to keep the animals awake during those 20 hours, the larger the sleep rebound appeared during the following four hours. Even after being awake the animals supposedly heightened SWA. This was particularly mentioned in their ‘wake’ EEG.

Cirelli added, “Slow-wave activity reflects the fact that sleep is regulated by homeostasis: in general, the longer we stay awake, the higher is SWA in the subsequent sleep. We knew that this was true after acute total sleep deprivation (for instance when we stay up all night); now we found that this is also true after chronic sleep restriction.”

It seems that observing SWA levels when the participants were wake is very crucial in understanding the impact of lack of sleep in detail. It was revealed that elevated SWA levels during periods of both sleeping and waking indicate the need to sleep. Variation in SWA levels was monitored in different areas of the brain. It has been predicted that this difference depends on what parts of the brain had been used during the waking period. The findings can possibly aid investigators in identifying the harmful effects of sleep deprivation in detail.

The research is published in the current online edition of Proceedings of the National Academy of Sciences.