Lead author An Pan, a research fellow in Harvard School of Public Health in Boston, and senior author Frank Hu, a professor of nutrition and epidemiology, analyzed data on more than 69,269 U.S. women, ages 42 to 67, in the Nurses' Health Study I, from 1988 to 2008, and 107,915 women, ages 25 to 42, in the Nurses' Health Study II, tracked from 1989 to 2007.
About 60 percent of the nurses performed more than one year of rotating night shift work at baseline. about 11 percent in Nurses' Health Study I had more than 10 years of rotating night shift work at baseline. About 4 percent in Nurses' Health Study II worked more than 10 years of rotating night shifts at baseline.
The study, published in the journal PLoS Medicine, found that the longer women worked rotating night shifts, the greater their risk of developing type 2 diabetes.
In addition, the study found, the women who worked rotating night shifts for three to nine years faced a 20 percent increased risk. Women who worked nights for 10 to 19 years had a 40 percent increased risk. Women who worked night shifts for more than 20 years were 58 percent more at risk.