Women who often work at night may face higher odds of developing type 2 diabetes, a new study suggests.
The study, which focused only on women, found that the effect got stronger as the number of years spent in shift work rose, and remained even after researchers accounted for obesity.
"Our results suggest that women have a modestly increased risk of type 2 diabetes mellitus after extended period of shift work, and this association appears to be largely mediated through BMI [weight]," concluded a team led by An Pan, a researcher in nutrition at the Harvard School of Public Health in Boston.
Prior studies have suggested that working nights disrupts circadian (day/night) rhythms, and such work has long been associated with obesity, the cluster of cardiovascular risk factors known as the "metabolic syndrome," and dysregulation of blood sugar.
Night shifts and diabetes
In the new study, researchers looked at data on more than 69,000 US women tracked from 1988 to 2008 as part of the Nurses Health Study. Almost 6,200 women developed type 2 diabetes over the course of the study.
Beginning at their entry into the study, women were asked how long they had worked rotating night shifts (including at least three nights of work per month).
The researchers found that the risk of developing type 2 diabetes rose with increasing duration of shift work. After adjusting for obesity, women who'd worked night shifts regularly for three to nine years faced a 6 % rise in risk, while women who had done so for 10 to 19 years saw their risk rise by 9%, and those who had worked such shifts for 20 years or more faced a 20% increase in risk.
Weight gain accounted for some, but not all, of the night shift-linked rise in diabetes risk, the team noted.
Experts note that research presented at meetings is typically considered preliminary until published in a peer-reviewed journal.
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