June 25, 2002 -- Eight hours of sleep is a luxury; six is enough to get you through, right? Wrong.
According to experts, getting just six hours of sleep a night is associated with increased daytime sleepiness, decreased performance, and a change in blood factors that promote the potentially dangerous process of inflammation.
"We found that ... six ... hours of sleep is not optimal [when compared with eight]," Alexandros N. Vgontzas, MD, tells WebMD. "Two hours of sleep deprivation per night for one week is associated with increased sleepiness, decreased performance, and activation of the inflammatory system." Vgontzas, a professor of psychiatry at Penn State College of Medicine in Hershey, is the author of a study on the effects of sleep deprivation presented at a recent medical meeting.
Most studies of the effects of sleep deprivation evaluate either total or severe sleep deprivation, allowing for less than five hours of sleep per night. Vgontzas asserts that there are few studies on the effects of modest sleep restriction, allowing for six hours of sleep, a pattern more closely resembling contemporary life.
This latest study evaluated the effects of eight hours of sleep vs. six hours of sleep on performance and blood factors associated with inflammation in 25 healthy volunteers.
The volunteers were observed in a sleep laboratory for 12 consecutive nights. The subjects were allowed to sleep for eight hours each night for the first four nights, and they were awakened at 6:30 a.m. Then, the volunteers underwent one week of sleep restriction, when they were awakened two hours earlier, at 4:30 a.m.
After just one week of sleep restriction, the volunteers had a significant increase of daytime sleepiness. Their levels of inflammatory factors jumped when they got only six hours of sleep, and they suffered from decreased vigilance and decreased ability to perform tasks that require coordination and thought.
The findings suggest that modest sleep deprivation may be associated with public safety concerns, such as traffic accidents, the investigators report. They also expressed concern that moderately sleep-deprived people may be at increased risk of major health hazards such as cardiovascular disease and osteoporosis.
"This is an excellent study," Marc R. Blackman, MD, tells WebMD. Blackman is the chief of the laboratory of clinical investigation at the National Center for Complementary and Alternative Medicine with the National Institutes of Health in Bethesda, Md., and was not involved in the study.
It would be interesting to see if these changes reversed when patients were returned to normal sleep patterns, he says.