According to study results published in BMJ, female nurses who frequently work rotating night shifts and adhere to an unhealthy lifestyle are at significantly greater risk of developing type 2 diabetes (T2D).
To determine the association between incident T2D and duration of rotating night shift work and lifestyle factors, researchers followed 143,410 women in the Nurses’ Health Study and Nurses’ Health Study II from 1988 to 2013. Included participants were free of T2D, cardiovascular disease, or cancer at baseline.
During follow-up, participants were asked to report any diagnosis of T2D, as well as their duration of rotating night shift work and lifestyle factors. The researchers defined rotating night shift work as ≥3 night shifts/month in addition to day and evening shifts. The lifestyle factors that were evaluated included diet, physical activity, smoking status, and body mass index.
Overall, there were 10,915 reported cases of incident T2D. The researchers discovered a positive association between duration of rotating night shift work and risk for diabetes diagnosis, with adjusted hazard ratios of 1.11 (95% CI, 1.00-1.22) for women with 1 to 5 years of rotating night shift work, 1.28 (95% CI, 1.10-1.49) for women with 5 to 9 years of rotating night shift work, and 1.46 (95% CI, 1.33-1.62) for women with ≥10 years of rotating night shift work (P <.001) compared with women without a history of working night shifts. A similar trend was identified for lifestyle health, with an adjusted hazard ratio of 2.30 (95% CI, 1.88-2.83) per unhealthy lifestyle factor (P <.001).
There was also a significant additive association between T2D and each 5-year increment of rotating night shift work plus each unhealthy lifestyle factor, with a hazard ratio of 2.83 (95% CI, 2.15-3.73) for their joint effect (P <.001). The attributable proportions of this joint effect were 17.1% for only rotating night shift work, 71.2% for unhealthy lifestyle, and 11.3% for their interaction.
Several limitations were noted for this study, such as an inability to generalize findings because of the homogeneity of the population of nurses.
The researchers said their findings suggest that “most cases of type 2 diabetes could be prevented by adherence to a healthy lifestyle, and the benefits would be larger in rotating night shift workers.”
Shan Z, Li Y, Zong G, et al. Rotating night shift work and adherence to unhealthy lifestyle in predicting risk of type 2 diabetes: results from two large US cohorts of female nurses [published online November 21, 2018]. BMJ. doi:10.1136/bmj.k4641