As if the night shift were not already unpleasant enough, a new study indicates that it may also increase your risk for developing type 2 diabetes.
The risk seems to be especially marked if you work a rotating shift for a long time.
“For nurses who spent a couple of years working rotating night shifts, there was a minimal increase in risk. But, for those with a very long duration of rotating shifts, the risk was almost 60 percent higher. This provides pretty strong evidence that the longer the rotating night shift work, the greater the risk of diabetes,” [Dr. Frank] Hu said.
Results of the study are published in the December issue of PLoS Medicine.Rotating shift work is becoming more common, according to background information in the study. Several studies have found a link between these varying or unusual work schedules and obesity and metabolic syndrome (a group of symptoms, such as high blood pressure and insulin resistance, linked to a higher risk of heart disease). Both factors are associated with an increased risk of type 2 diabetes. Recently, a few studies on Japanese men found a link between working the night shift and type 2 diabetes, according to the study.
For the current study, rotating shift work was defined as working three or more nights a month, plus days and evenings. Hu and his team looked at data from two groups of women involved in the U.S. Nurses’ Health Studies I and II. There were more than 69,000 women between the ages of 42 and 67 in the first study, and nearly 108,000 women between the ages of 25 and 42 in the second study.
When the women enrolled in the trials, none had diabetes, cardiovascular disease or cancer.
During the 18- to 20-year study period, 6,165 women in the first group and almost 4,000 women from the second group developed type 2 diabetes.
When compared to women who hadn’t done rotating shift work, women who did one to two years of shift work had a 5 percent increase in type 2 diabetes. Women who worked shifts for three to nine years had a 20 percent increased risk, while women who toiled 10 to 19 years on rotating shifts had a 40 percent greater risk of type 2 diabetes compared to women who didn’t do shift work.
Women with more than 20 years on a rotating work schedule had the highest risk of all, with a 58 percent increase in the risk of type 2 diabetes, the study found.
It’s still possible that it’s not the night shift per se that causes the problem, though:
“This study shows an association between working night shifts and obesity and diabetes. But, it’s difficult to disassociate other risk factors,” Zonszein said. “It may not just be that they work at night. They may work harder; they may be more stressed. There was more smoking. All of these things are related.”