Rotating night-shift work associated with type 2 diabetes risk in women

Pan A. PLoS Med. 2011;doi:10.1371/journal.pmed.1001141.

Issue: January 2012

Female rotating night-shift workers may be at an increased risk for type 2 diabetes and, therefore, greater weight gain, according to data from a Harvard study.

Researchers assessed data for two cohorts of women: those in the Nurses’ Health Study (NHS) I aged 42 to 67 years (n=69,269) and those in the NHS II aged 25 to 42 years (n=107,915). Follow-up lasted from 18 to 20 years. In the first cohort, 6,165 women developed type 2 diabetes; in the second, 3,961 developed the disease.

Rotating night shifts were defined as at least 3 nights per month, plus days and evenings in that month. Women were asked about the length of time they worked these shifts, and in NHS II, the information was updated every 2 to 4 years.

Night-shift work was associated with an increased risk for type 2 diabetes in both cohorts (P<.001). The HRs were compared for those who did not report rotating night-shift work vs. those who worked various time periods (see Table).

Rotating night-shift work	NHS I	NHS II
1-2 years	0.99 (95% CI, 0.93-1.06)	1.13 (95% CI, 1.04-1.23)
3-9 years	1.17 (95% CI, 1.10-1.25)	1.34 (95% CI, 1.23-1.45)
10-19 years	1.42 (95% CI, 1.29-1.55)	1.76 (95% CI, 1.57-1.96)
>20 years	1.64 (95% CI, 1.46-1.83)	2.50 (95% CI, 2.00-3.14)

Adjusting for updated BMI attenuated the association, although it was still significant: pooled HRs were 1.03 (95% CI, 0.98-1.08) for 1 to 2 years of work; 1.06 (95% CI, 1.01-1.11) for 3 to 9 years of work; 1.10 (95% CI, 1.02-1.18) for 10 to 19 years of work; and 1.24 (95% CI, 1.13-1.37) for more than 20 years of work.

“Additional studies are needed to confirm our findings in men and other ethnic groups and to further investigate the underlying mechanisms for the association,” the researchers wrote. “Because a large proportion of the working population is involved in some kind of permanent night and rotating shift work, our study has potential public health significance. Recognizing that rotating night-shift workers are at a higher risk of type 2 diabetes should prompt additional research into preventive strategies in this group.”

Follow EndocrineToday.com on Twitter.