In addition to rotating night shift work being associated with obesity and increased heart disease, a study of two large cohorts of women in the U.S. showed that it a history of night shift work is also associated with a modestly increased risk of type 2 diabetes.
The study considered rotating night shifts to be at least three nights a month in addition to 19 days and evenings. The researchers used data from the 1976 and 1989 Nurses’ Health Studies and compared those who had a history of rotating night shift work to a group who did not. In total there were roughly 175,000 nurses included in the study over a period of nearly two decades.
The researchers were able to determine that “the duration of rotating night shift work was strongly associated with an increased risk of type 2 diabetes.” Although this study only used women, another report found a higher prevalence of diabetes among male Japanese workers who had a history of rotating night shifts.
There are several causes of an increased risk of diabetes, one being the disruption of circadian rhythms regulating a range of biological processes.
In general, the nurses who regularly worked rotating night shifts reported weight gain, although there is usually a small difference in nutritional intake when comparing shift workers to daytime works. However, the shift workers often shift the time of intake, which could influence biological processes that increase body mass.
Also, the women who had worked more years of rotating night shifts were more likely to be current smokers compared to the group of nurses who didn’t have a history of rotating night shift work.