Sleeping for less than six hours
or for more than nine hours each night is associated with
an increased risk of diabetes and impaired blood sugar
(glucose) tolerance, researchers report in this week's
issue of the Archives of Internal
Medicine.
"There are a lot of people
who sleep five or six hours per night who we generally
think are not getting enough sleep," lead author Dr. Daniel
J. Gottlieb stated. His group hypothesized that people
who do not get enough sleep may be at increased risk of
developing diabetes or impaired glucose tolerance.
Gottlieb, of Boston University
School of Medicine, and colleagues enrolled 1,486 subjects,
ages 53 to 93 years, in their study. The subjects completed
questionnaires regarding sleep patterns and underwent
fasting glucose and glucose tolerance testing.
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.
"These are strong associations
suggesting that voluntary sleep restriction may cause
impaired glucose regulation," Gottlieb said. "Probably
those sleeping nine hours or more per night are doing
so because of some underlying condition that may not be
diagnosed but that puts them at increased risk of diabetes,"
he suggested.
The authors also noted
that adequate levels of sleep should be tested as a non-drug
treatment strategy in patients with diabetes or impaired
glucose tolerance.
Sleeping for at least seven
hours a night, Gottlieb concluded, "is a good health practice
for a variety of reasons, and this is one more reason."
SOURCE: Archives of Internal
Medicine, April 25, 2005.
