SAN FRANCISCO (Reuters Health) - Just a few hours of sleep deprivation could impair daily functioning and affect hormonal levels in the body, researchers reported here Saturday at the annual meeting of the Endocrine Society.

"Even modest sleep restriction affects hormones," said Dr. Alexandros Vgontzas, a professor of psychiatry at Pennsylvania State University in Hershey.

While severe sleep deprivation has been repeatedly shown to have harmful effects on mental and physical functioning, many scientists do not believe mild amounts of curtailed sleep will do much damage. "They believe it is no big deal," Vgontzas noted. "We decided to mimic real life by restricting normal sleep by two hours for a week."

Vgontzas and colleagues at the National Institutes of Health studied 25 young healthy men and women who agreed to spend 12 consecutive days in a sleep laboratory. The first four nights, they were allowed to sleep for up to eight hours. The remaining nights, the study participants were woken after they slept for six hours.

After a week of mild sleep deprivation, the researchers measured changes in study participants' quality of nighttime sleep, daytime drowsiness, hormonal activity as measured by continuous blood sampling and hourly performance on a vigilance test.

After one week of sleep deprivation, as expected, the study participants fell asleep faster and slept more deeply, a sign of the body's attempt to adapt to the sleep loss. And during the daytime, the sleep-deprived individuals showed more signs of sleepiness and performed worse on a vigilance test.

In addition, researchers found that sleep deprivation affected hormonal levels. Men and women had a 40% to 60% average increase in the inflammatory marker interleukin-6 (IL-6), while men alone showed a 20% to 30% increase in another marker for inflammation, tumor necrosis factor (TNF). Both IL-6 and TNF are cytokines, which are proteins the body releases in response to injury.

"Women seemed to fare better; they were more resilient," Vgontzas noted. In addition to not producing higher levels of TNF, they were able to sleep more soundly, getting 70 minutes of deep sleep, or rapid eye movement (REM) sleep, compared to the 40 minutes obtained by men.

The findings indicate that getting a full night's rest of eight hours on top of a base of six or so hours is not a nice bonus, but necessary, Vgontzas said. "There is no 'optional' sleep," he said. "Those two to three hours are important for functioning during the day."

In addition, the finding that lack of sleep may stimulate an increase in chronic, low-level inflammatory response is worrisome, because that state has been linked to conditions such as high blood pressure, heart disease and most recently, diabetes, Vgontzas said. "Restriction of sleep a few hours is a major risk for public safety," he warned.

Reference Source 89

For more information on how to prevent other diseases, use
PreventDisease.com's "Quick Prevention Resources".