Night Shift Work May Raise Diabetes Risk

December 6, 2011


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By Amanda Gardner

TUESDAY, December 6, 2011 ( — Women whose jobs require them to rotate through day and night shifts may be increasing their diabetes risk, especially if they maintain that schedule over a long period of time, a new study of nurses suggests.

A woman’s risk of developing type 2 diabetes increases steadily with the years of shift work she puts in, the study found. Compared to nurses who worked days only, those who worked periodic night shifts for as little as three years were 20% more likely to develop type 2 diabetes, while those who clocked at least 20 years of shift work were nearly 60% more likely to develop the disease.

“The increased risk is not huge, but it’s substantial and can have important public health implications given that almost one-fifth of the workforce is on some kind of rotating night shift,” says senior author Frank Hu, MD, a professor of nutrition and epidemiology at the Harvard School of Public Health, in Boston.

Much of the increase in diabetes risk can be explained by weight gain—a common and well-known side effect of shift work, which disrupts eating and sleeping schedules in ways that can make following a healthy lifestyle a challenge. But other, more subtle disturbances may also play a role.

Irregular work hours tend to disrupt the body’s circadian rhythms (also known as the “body clock”), which play a critical role in maintaining healthy blood-sugar metabolism and energy balance, Hu says. Previous studies in both humans and animals have shown that sleep deprivation and irregular sleep-wake cycles can lead to insulin resistance and rising blood-sugar levels—both hallmarks of diabetes.

Our internal clock may influence our ability to metabolize certain foods at certain times, says David J. Earnest, PhD, a professor of neuroscience and experimental therapeutics at the Texas A&M Health Science Center College of Medicine, in College Station.

If you raid the refrigerator for a late-night snack of ice cream, the enzymes and systems needed to turn high-fat foods into energy may not be alert enough to handle the barrage, and as a result those calories may end up as fat rather than fuel, Earnest says. Similarly, he adds, a meal of bacon and eggs may be less healthy if eaten after sundown than after sunrise.

“In the past 25 years, we’ve focused a lot on lifestyle issues such as maintaining a healthy diet and avoiding a sedentary lifestyle,” Earnest says. “But regardless of whether you’re a shift worker or not, that may not be enough to avoid these health issues.”

Next page: Shift workers not the only ones at risk

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