Night-shift workers, poor sleepers at risk for diabetes

Third-shift workers or those with poor sleep habits might be at higher risk of developing diabetes mellitus, according to a new study that links circadian misalignment to impaired insulin sensitivity.

The study, led by Kenneth Wright, PhD, a professor at the University of Colorado and director of the Sleep and Chronobiology Laboratory, shows that people who are awake at night may have decreased insulin sensitivity because the body is not prepared for activity of food intake during the biological night.

“A patient's risk of diabetes is increased by short sleep schedules due to being awake during the biological night when the body clock is not prepared for nutrition intake,” Wright tells Medical Economics.

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The study used two teams of healthy men and women in their 20s who ate nutritional diets prior to the short-night sleep period, then were allowed to eat the types and amounts of foods they wanted during the study period. The study period permitted one group of participants 5 days with just 5 hours of sleep each night, followed by 5 days with 9 hours of sleep each night. The other group did the opposite–5 days of 9 hours of sleep followed by 5 days of just 5 hours of sleep.

Researchers found that the nights in which participants slept just 5 hours resulted in a 20% reduction in both oral and intravenous insulin sensitivity in otherwise healthy study subjects. After the short-night periods, it took 3 consecutive nights of 9 hours of sleep to restore oral insulin sensitivity, according to the study.

“Our study and other previous studies have shown sleep loss reduces sensitivity to insulin, but we also found in this study that the test subjects with sleep loss had to release a lot more insulin to keep their blood sugar levels normal,” Wright says, adding that more research is needed to determine the effects on other demographic groups that might be even more sensitive to the effects of poor sleep patterns. “These were young and very healthy people we studied. We don’t know how much this might affect middle-aged or elderly people.”

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Wright’s study suggests that the change in insulin sensitivity may be related to the fact that wakefulness when melatonin levels were still high-meaning the body is still promoting sleep-contributes to metabolic dysregulation related to food intake during the biological night.

Other studies have also connected shift-work or poor sleep habits to increased diabetes risks, including a 2011 report from Brigham & Women's Hospital and Harvard Medical School that revealed peak glucose levels were 16% higher, and insulin levels were 40% to 50% higher after meals after just one night shift compared to levels found in day shift workers.

For physicians, these studies drive home the importance of screening patients who work nights or sleep irregular hours for diabetes, in addition to patients with other well-known risk factors.