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Chronic short sleep, long sleep raise risk for type 2 diabetes in older women
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Middle-aged and older women who sleep for 6 hours or less per night or increase their average sleep time by 2 hours or more over several years have an increased risk for developing type 2 diabetes, according to research in Diabetologia.
Elizabeth M. Cespedes, SM, from the Harvard School of Public Health, and colleagues analyzed data from 59,031 women aged 55 to 83 years without diabetes participating in the Nurses’ Health Study in 2000. Researchers measured the difference between participants’ reported 24-hour sleep duration in 1986 and in 2000, whereas diet, physical activity and other covariates were updated every 2 to 4 years. Participants self-reported diabetes status via questionnaires.
Researchers used adjusted Cox regression analysis for 1986 sleep duration and 1986 values for diabetes risk factors. Through 2012, researchers documented 3,513 incident cases of diabetes; 49% of women reported sleeping 7 to 8 hours per night in both 1986 and 2000, whereas 15% consistently reported being short sleepers (less than 6 hours) and 2% consistently long sleepers (more than 9 hours). Within the cohort, 5% reported decreases in sleep time of 2 hours or more during the 14-year study period; 7% reported sleep increases of 2 hours or more.
Both decreases and increases in sleep time were associated with greater diabetes risk, although the risk for decreases in sleep did not persist after adjustment. After adjustment for race, diabetes family history, shift work, BMI and other factors, researchers found that increases in sleep time between 1986 and 2000 were significantly associated with a greater risk for diabetes, with an HR of 1.15 (95% CI, 1.01-1.3).
Researchers also cross-classified women according to sleep duration in 1986 and 2000 and found that women with chronic short sleep, or who initially reported less than 6 hours per day but then increased sleep duration, had an elevated risk for diabetes (HR = 1.21; 95% CI, 1.1-1.35) compared with women maintaining an average sleep duration of 7 to 8 hours per night (HR = 1.1; 95% CI, 1.001-1.21). After adjustment for BMI, only the risk associated with increased sleep duration persisted, according to researchers.
“While chronic short sleep duration was associated with higher risk [for] diabetes in our study, our results are not consistent with the hypothesis that short or long sleepers who achieve normative sleep durations will experience benefits for metabolic health,” the researchers wrote. “Instead, we found that extreme increases (and not decreases) in sleep duration were associated with weight gain and increased risk [for] diabetes, independent of prior sleep duration.”
Researchers also observed modest, adverse associations between sleep duration, diet quality and physical activity, but diet and physical activity did not mediate the association between increased sleep duration and diabetes. – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.
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