Overnighters beware! Third-shift work raises risk of type 2 diabetes

Working overnight, in both permanent and rotating shifts, is associated with a higher risk of developing type 2 diabetes, regardless of genetic risk, according to a new study published in Diabetes Care.

“Shift work, particularly night shifts, disrupts social and biological rhythms, as well as sleep, and through those pathways has been suggested to increase the risk of metabolic disorders and specifically type 2 diabetes,” wrote first author Celine Vetter, PhD, University of Colorado in Boulder, and colleagues.

Using the U.K. Biobank data, researchers on both sides of the Atlantic sought to examine effects of past and current night shift work and genetic type 2 diabetes vulnerability.

The research cohort consisted of more than 272,000 day workers and more than 70,400 night shift workers. The day workers sample included more than 6,700 cases of type 2 diabetes.

Researechers analyzed information including age, gender, race, family history of diabetes, alcohol use, physical activity, smoking, mental health symptoms and sleeping habits, among other characteristics.

“Overall, shift workers were younger, were more materially deprived, worked longer hours and were more physically active compared with day workers,” Vetter et al. wrote. “Shift workers were also more likely to be male, be of non-European ancestry, have a family history of type 2 diabetes, smoke and consume alcohol daily.”

The researchers noted rotating night shift workers were more likely to have type 2 diabetes than their counterparts. The team found those who worked rotating shifts that included night shifts were 44 percent more likely to have type 2 diabetes versus those who only worked day shifts.

The data also suggested that working more night shifts per month was associated with higher type 2 diabetes odds. Night shift work less than three times a month increased the risk by 24 percent, and night shift work more than eight times a month increased odds by 36 percent.

Lastly, the researchers noted that night shift work did not interact with genetic type 2 diabetes predisposition and did not exacerbate type 2 diabetes odds.

“Overall, our results add to the current body of literature in that they suggest that reducing night shift work frequency might represent another avenue to improve metabolic health during working life and beyond,” the authors concluded.