The data published in the March issue of Diabetes Care were obtained from 1,709 men, 40 to 70 years old. The men were enrolled in the Massachusetts Male Aging Study and were followed for 15 years with home visits, a health questionnaire and blood samples.
Six to eight hours of sleep was found to be most healthy. In contrast, men who reported they slept between five and six hours per night were twice as likely to develop diabetes and men who slept more than eight hours per night were three times as likely to develop diabetes, according to the lead author, H. Klar Yaggi, M.D., professor in Yale's Department of Internal Medicine, pulmonary section. Previous data from the Nurses Health Study have shown similar results in women.
"These elevated risks remained after adjustment for age, hypertension, smoking status, self-rated health status and education," Yaggi said.
He said researchers are just beginning to recognize the hormonal and metabolic implications of too little sleep. Among the documented effects, Yaggi said, are striking alterations in metabolic and endocrine function including decreased carbohydrate tolerance, insulin resistance, and lower levels of the hormone leptin leading to obesity. The mechanisms by which long sleep duration increase diabetes risk requires further investigation.
"There is a lot of interest in determining whether sleep disturbances such as a reduced amount of sleep or disorders like sleep apnea may actually worsen the metabolic syndrome," said Yaggi. Metabolic syndrome is a cluster of risk factors including high blood pressure, obesity, high cholesterol and insulin resistance which increase the risk for heart disease and stroke.
Co-authors include Andre Araujo and John McKinlay. The research was supported in part by the National Institute on Aging, the National Institute of Diabetes and Digestive and Kidney Disorders, the Yale Mentored Clinical Research Scholars Program from the National Center for Research Resources, and a career development award from the Veterans Affairs Health Services and Research and Development Service.
Diabetes Care 29: 657-661 (March 2006)
Journal
Diabetes Care