Diabetes Loves the Graveyard Shift

Type 2 diabetes risk linked to long term rotating night shift work

(RxWiki News) It can be exhausting to work an irregular schedule with both night and day shifts. An irregular schedule also may raise the risk of developing type 2 diabetes.

Women who work a rotating schedule - which involves at least three night shifts per month on top of day and evening shifts - may be more at risk of developing type 2 diabetes than women who work only day or evening shifts.

"Your work schedule affects your health."

Past research has looked at the relationship between shift work and the risk of cancer and heart disease. For this study, An Pan, Ph.D., a research fellow at the Harvard School of Public Health, wanted to look at the association between shift work and type 2 diabetes. Their study was also the first large study to look at women.

Their findings show that women who work long-term rotating shifts that include at least three night shifts per month, in addition to day shifts during that same month, may have a greater risk of type 2 diabetes, compared to women who work only days and evenings.

"Long-term rotating night shift work is an important risk factor for the development of type 2 diabetes," says Dr. Pan. He also notes that this risk grows with the number of years that a woman works rotating shifts.

To come to these results, Dr. Pan and colleagues looked at data from more than 69,000 women involved in the Nurses' Health Study I and nearly 108,000 women in the Nurses' Health Study II. The women in the Nurses' Health Study I were between 42 and 67 years of age.

Those in the Nurses' Health Study II were between 25 and 42 years of age. About 11 percent in the Nurses' Health Study I and four percent in the Nurses' Health Study II had worked more than 10 years of rotating night shifts.

The researchers found that the women's risk of type 2 diabetes increased the longer they worked rotating night shifts. If they worked rotating night shifts for three to nine years, their risk of diabetes increased by 20 percent. Working rotating night shifts for 10 to 19 years increased the risk by 40 percent. The risk of diabetes increased by 58 percent for those who worked rotating night shifts for more than 20 years.

They also found that women who worked rotating night shifts put on more weight and had a greater chance of becoming obese. As obesity is the major cause of type 2 diabetes, this increased weight gain may partially explain for the increased risk of diabetes.

With so many U.S. workers who work rotating night shifts, these findings have a huge significance for public health. However, before experts can act on these findings, more research is needed. The results need to be confirmed in men and some other ethnic groups.

Researchers also need to gain a better understanding of the mechanisms that create the link between irregular shift work and type 2 diabetes.

According to senior author, Frank Hu, M.D., M.P.H., Ph.D., of the Harvard School of Public Health, "This study raises awareness of increased obesity and diabetes risk among night shift workers and underscores the importance of improving diet and lifestyle for primary prevention of type 2 diabetes in this high risk group.

This study was supported in part by the National Institutes of Health and by awards from the National Heart, Lung, and Blood Institute. The results are published in the journal PLoS Medicine

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Review Date: 
December 9, 2011