Insufficient Nightly Sleep May Raise Risk of Diabetes

From Reuters Health Information

NEW YORK (Reuters Health) Aug 11 - An inadequate amount of nightly shut-eye, coupled with physical inactivity and overeating, may fuel the development of insulin resistance and reduced glucose tolerance, results of a new study indicate.

"Our findings suggest that combining the unhealthy aspects of the Westernized lifestyle with insufficient sleep may add to the risk of overweight and sedentary individuals to develop diabetes," Dr. Plamen Penev of the University of Chicago, Illinois, and a senior author of the study, told Reuters Health.

The findings stem from a randomized controlled crossover study involving 11 healthy but sedentary middle-aged men and women (mean BMI, 26.5) who reported sleeping 7.6 hours daily.

The study subjects participated in two controlled 2-week periods of sedentary living with ad libitum food intake and 5.5 or 8.5 hours in bed per night. As nightly time in bed changed from 8.5 to 5.5 hours, subjects went to bed later and got out of bed earlier and, as a result, mean sleep duration was reduced by 122 minutes a day. At the end of each intervention, the study subjects took oral and intravenous glucose challenge tests.

According to the report in the September issue of the Journal of Clinical Endocrinology and Metabolism, recurrent sleep restriction (5.5 hours) led to reduced oral glucose tolerance (p < 0.01) and insulin sensitivity (p < 0.03), and increased glucose effectiveness (p < 0.04).

Both sleep times (5.5 hours and 8.5 hours) led to comparable weight gain in these sedentary overeating adults.

Sleep restriction also led to a modest increase in 24-hour epinephrine and nighttime norepinephrine levels, whereas 24-hour cortisol and growth hormone concentrations remained unchanged.

"This is the first controlled experiment to document that recurrent bedtime restriction, which approximates short sleep times experienced by many people in everyday life, can result in decreased oral glucose tolerance," the researchers note in their report.

Additional studies, they say, are needed to study the impact of habitual sleep curtailment on glucose metabolism under normal "free-living" conditions.

"If confirmed by future larger studies, these results would indicate that a healthy lifestyle should include not only healthy eating habits and adequate amounts of physical activity, but also obtaining a sufficient amount of sleep," Dr. Penev said.

J Clin Endocrinol Metab 2009.