Rotating Shift Work Raises Diabetes Risk

Rotating shift work is becoming more common, but new research says that it may increase the risk of developing type 2 diabetes. And the longer you work a rotating shift, the greater your risk.

"For those with a very long duration of rotating shifts, the risk was almost 60 percent higher," says study author Frank Hu, M.D., at the Harvard School of Public Health. "This provides pretty strong evidence that the longer the rotating night shift work, the greater the risk for diabetes."

Dr. Hu and his team looked at data from more than 177,000 women ages 42 to 67 who were part of the U.S. Nurses' Health Studies. None of the women had diabetes, cardiovascular disease, or cancer when they enrolled in the research program.

Diabetes diagnosed

During the 18- to 20-year study period, more than 10,000 women developed type 2 diabetes. Those who did one to two years of rotating night shift work had a 5 percent increase in type 2 diabetes. Rotating night shift work was defined as working three or more nights a month, plus days and evenings.

The risk increased as the number of shift-work years grew. Women who spent 10 to 19 years working a rotating shift had a 40 percent greater risk for type 2 diabetes, compared with those 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 for type 2 diabetes.

The study was published in the journal PLoS Medicine.

Body's time clock

Dr. Hu says that more research is needed to determine why rotating shift work might increase the risk for type 2 diabetes, but he says the cause is likely both biological and behavioral. When the body's natural time clock, or circadian rhythm, is disrupted, its ability to balance energy needs gets mixed up. This can cause higher levels of glucose and insulin resistance, which are hallmarks of type 2 diabetes.

Working on rotating shifts also affects eating and sleeping. The researchers also found that the study participants working rotating shifts tended to smoke more.

Nearly 26 million Americans have diabetes. Most have type 2 diabetes, typically caused by excess body weight and physical inactivity. Over time, the disease can damage vital organs, including the kidneys, nerves, and heart.

Always talk with your health care provider to find out more information.