Sleeping too little or too much may increase risk of diabetes

A new report says that people who sleep for less than six hours or for more than nine hours each night may have an increased risk of diabetes and impaired blood sugar (glucose) tolerance.

Researchers at Boston University School of Medicine studied 1,486 subjects, ages 53 to 93 years who completed questionnaires regarding sleep patterns and underwent fasting glucose and glucose tolerance testing. They found that diabetes was present in 20.9 percent of subjects and impaired glucose tolerance was present in another 28.2 percent. A usual sleep time of six hours or less was reported by 27.1 percent, including 8.4 percent who reported five hours or less. A total of 8.6 percent said that they slept for nine hours or more.

Compared with subjects who slept for seven to eight hours each night, the risk of diabetes was increased by 2.5-fold in those sleeping five or less hours, 1.66-fold for those sleeping six hours, and 1.79-fold for those sleeping nine or more hours. The corresponding increased risks of developing impaired glucose tolerance were 1.33-, 1.58-, and 1.88-fold. Blood glucose levels were not significantly affected by insomnia.

Lead author Dr. Daniel J. Gottlieb says many people who sleep five or six hours per night are generally thought of as not getting enough sleep and hypothesizes that people who do not get enough sleep may be at increased risk of developing diabetes or impaired glucose tolerance.

He suggests there are strong implications that voluntary sleep restriction may cause impaired glucose regulation, and it is possible that those who sleep nine hours or more per night do so because of some undiagnosed underlying condition that may put them at increased risk of diabetes.

The researchers say that adequate levels of sleep should be tested as a non-drug treatment strategy in patients with diabetes or impaired glucose tolerance.

In conclusion Gottlieb says that sleeping for at least seven hours a night "is a good health practice for a variety of reasons, and this is one more reason."

Archives of Internal Medicine, April 25, 2005.