Sleep Patterns and Diabetes: Nurses’ Health Study Reveals Link
By Debra Wood, RN, contributor
Research about the relationship between sleep and diabetes dates back years, and new findings from the Nurses’ Health Study add to the body of knowledge. Researchers have found that increases in sleep duration are associated with a greater risk of developing type 2 diabetes among middle-aged and older women.
“Our research is consistent in many ways with what others have found,” said Elizabeth Cespedes, ScD, at the Harvard T.H. Chan School of Public Health in Boston and Kaiser Permanente Northern California in Oakland. “The unique features of our study were that we examined, first, long-term changes in sleep duration among women observed over almost two decades; and second, we examined whether weight gain, diet quality and physical activity changes explained the sleep-diabetes relationship.”
Cespedes and colleagues assessed changes in sleep and development of type 2 diabetes in a 59,031 women cohort participating in the Nurses’ Health Study. Participants reported sleep duration in 1986 and 2000. The team excluded women who had diabetes prior to 2000 or were missing responses to sleep duration questions on the survey.
Then they compared changes in sleep duration and found an association between sleep and the development of type 2 diabetes, after adjusting for changes in diet, physical activity and weight.
“We found chronic short-sleep duration--less than or equal to 6 hours per day--as well as large increases in sleep duration of 2 or more hours per day were associated with higher risk of diabetes,” Cespedes said.
During the study period, 3,513 women developed diabetes. Average sleep duration did not change. Only 12 percent reported changes in sleep duration of two or more hours. Those who did report the 2-hour or greater changes in the amount of time they slept also reported higher body mass, being less physically active and eating a less-healthy diet. They also were more likely to indicate they smoked, snored, had hypertension, elevated cholesterol levels, had a family history of diabetes, were taking an antidepressant, or worked shift work for five or more years. Those who reported 2 hours of sleeping longer in 2000 than 1986 experienced greater weight gain than other women.
The study found a link between extreme increases in sleep duration and the development of diabetes, regardless of prior sleep duration patterns. Sleeping more hours in later life did not mitigate the risk associated with short sleep and diabetes.
The National Institutes of Health provided funding for the study, which was reported in Diabetolgia. The authors wrote that it is the largest longitudinal, long-term study to date examining whether diet and physical activity affect changes in sleep patterns and diabetes.
Cespedes explained, “Most studies have examined a single, baseline measurement of sleep duration and observed later outcomes. When this is done, there is a U-shaped relationship with both short sleep, typically less than 6 hours per night, and long sleep, typically longer than 9 hours per night, increasing risk of diabetes.”
Additional, there have been experiments that restricted sleep duration for a brief period in a laboratory and examine short-term outcomes such as glucose tolerance.
“This type of intervention study is a very rigorous design, but it cannot tell us about the influence of long-term sleep habits on later chronic disease outcomes,” Cespedes explained.
More needs to be learned about the association between sleep and diabetes.
“To nurses I would say the following: Taken together, this body of research suggests that, first and most importantly, long-term maintenance of healthy sleep duration can aid in chronic disease prevention,” Cespedes concluded. “Second, it is possible that very long sleep durations or large increases in sleep duration may be indicative of ill health in patients.”
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