Less than Six Hours of Shut-Eye Increases Risk of Developing Diabetes, Study Finds

BUFFALO, N.Y. -- If you need an excuse to turn in early, results of University at Buffalo research provides a good one.

A study published online ahead of print in the Annals of Epidemiology shows that people who slumber less than six hours a night during the work week were three times more likely to have elevated levels of blood sugar than those who slumber six-to-eight hours.

"This research supports growing evidence of the association of inadequate sleep with adverse health issues," says the study's first author Lisa Rafalson, PhD, a National Research Service Award (NRSA) Fellow in the UB Department of Family Medicine, UB School of Medicine and Biomedical Sciences.

Rafalson now is on the faculty of D'Youville College in Buffalo, with volunteer appointments in UB pediatrics, family medicine and social and preventive medicine departments.

"To our knowledge no other studies have reported specifically on the association of sleep and impaired fasting glucose, but our estimates are in line with studies that examined the association of sleep, impaired glucose tolerance and type 2 diabetes.

"Impaired fasting glucose – a glucose level between 100–125 mg/dl is known as pre-diabetes, and about 25 percent of people who have impaired fasting glucose will, at some point, develop type 2 diabetes," Rafalson says.

The researchers suggest several mechanisms that could play a role in the relationship of sleep loss and increased glucose levels, noting that previous experiments have shown that severely restricting sleep can result in an increase in appetite-stimulating hormones and a decrease in hormones that inhibit appetite, as well as increased hunger for calorie-dense foods.

Sleep restriction also decreases glucose tolerance and increases cortisol levels and variations in heart rate, says Rafalson -- changes that can interfere with regulation of plasma glucose, which results in increased blood glucose levels.

Other mechanisms that may be in play involve the sympathetic nervous system, as well as an increase in inflammatory factors, which are well known to increase diabetes risk, the study reports.

Rafalson's findings are based on data from a six-year follow-up of participants who initially took part in the Western New York Health Study, conducted from 1996 to 2001 by UB's Department of Social and Preventive Medicine.

The 91 persons with normal fasting glucose levels at baseline who developed pre-diabetes by their follow-up exam were matched with study participants who had maintained normal glucose levels.

Participants were placed into three groups based on the their Sunday through Thursday average daily amount of sleep: "short-sleepers," who reported less than six hours of sleep nightly; "long-sleepers," who reported sleeping more than eight hours nightly; and a reference group who slept six-to-eight hours a night.

Results show that "short-sleepers" had a significantly increased risk of progressing from normal glucose levels to pre-diabetes, compared to those who slept six-to-eight hours nightly.

The study found that sleeping an average of more than eight hours a night also increased the likelihood of developing increased fasting glucose, consistent with other literature, but the findings weren't statistically significant, possibly because only five people were in that group, Rafalson noted.

"A high glucose level is associated with many complications, such as heart disease and premature death," says Rafalson. "Physicians should discuss sleep habits with their patients, along with other lifestyle issues that are important to long-term health, such as diet and exercise."

Additional UB contributors to the study are Richard P. Donahue, PhD, MPH, Michael J. Lamonte, PhD, MPH, and Joan Dorn, PhD, all from the UB School of Public Health and Health Professions. Contributors to the study who now are at other institutions are Saverio Stranges, MD, PhD, Jacek Dmochowski, PhD, and Maurizio Trevisan, MD.

The study was supported by a grant from the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health.

The University at Buffalo is a premier research-intensive public university, a flagship institution in the State University of New York system and its largest and most comprehensive campus. UB's more than 28,000 students pursue their academic interests through more than 300 undergraduate, graduate and professional degree programs. Founded in 1846, the University at Buffalo is a member of the Association of American Universities.