Researchers at the University of Chicago have found a relationship between a lack of deep sleep and development of type-2 diabetes. Healthy individuals who have their slow-wave sleep pattern disrupted for as few as three days in a row a reduction in how their bodies' process insulin as if they had gained 20-30 pounds. The paper is scheduled for release in the Proceedings of the National Academy of Sciences January 2.

Type-2 diabetes is often associated with obesity and aging, and is caused by the body being resistant to insulin. Insulin is a hormone that permits the transfer of blood sugar into cells. Ninety to 95 percent of all cases of diabetes in North America are type-2 cases. Slow-wave sleep is associated with REM (rapid-eye movement) sleep and dreaming.

The study had nine participants, aged 20 and 31, five men and four women, who were all lean and in good health. Researchers in the lab of Eve Van Cauter, professor of medicine at the University of Chicago established baseline data on the uptake of insulin following 8.5 hours of sleep, then disrupted their sleep for several nights using a sound loud enough to jolt them out of slow wave sleep, but not loud enough to bring them to full wakefulness.

Subjects were then given a solution of glucose, and their insulin reaction measured. After slow-wave sleep deprivation, they found that while the subjects needed additional insulin to process the glucose, their body failed to react properly and produce enough.

"These findings demonstrate a clear role for slow-wave sleep in maintaining normal glucose control," said the study's lead author, Esra Tasali, MD, assistant professor of medicine at the University of Chicago Medical Center in a press release. "A profound decrease in slow-wave sleep had an immediate and significant adverse effect on insulin sensitivity and glucose tolerance."

Van Cauter's work follows on research by Fred W. Turek, Ph.D., and Joseph Bass, M.D., Ph.D., of Northwestern University in Evanston, Illinois, in which they found a similar effect in mice in 2005.

"Since reduced amounts of deep sleep are typical of aging and of common obesity-related sleep disorders, such as obstructive sleep apnea these results suggest that strategies to improve sleep quality, as well as quantity, may help to prevent or delay the onset of type 2 diabetes in populations at risk," Van Cauter said.

The work was funded by the National Institutes of Health, which operates the Clinical and Integrative Diabetes and Obesity Study devoted to diabetes research.

Additional authors include Rachel Leproult and David Ehrmann of the University of Chicago Medical Center.