• Zhilei Shan, Yanping Li, Geng Zong, Yanjun Guo, Jun Li, JoAnn E Manson, Frank B Hu, Walter C Willett, Eva S Schernhammer, and Shilpa N Bhupathiraju.
• Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China zshan@hsph.harvard.edu.
• BMJ. 2018 Nov 21; 363: k4641.

ObjectivesTo prospectively evaluate the joint association of duration of rotating night shift work and lifestyle factors with risk of type 2 diabetes risk, and to quantitatively decompose this joint association to rotating night shift work only, to lifestyle only, and to their interaction.DesignProspective cohort study.SettingNurses' Health Study (1988-2012) and Nurses' Health Study II (1991-2013).Participants143 410 women without type 2 diabetes, cardiovascular disease, or cancer at baseline.ExposuresRotating night shift work was defined as at least three night shifts per month in addition to day and evening shifts in that month. Unhealthy lifestyles included current smoking, physical activity levels below 30 minutes per day at moderate to vigorous intensity, diet in the bottom three fifths of the Alternate Healthy Eating Index score, and body mass index of 25 or above.Main Outcome MeasuresIncident cases of type 2 diabetes were identified through self report and validated by a supplementary questionnaire.ResultsDuring 22-24 years of follow-up, 10 915 cases of incident type 2 diabetes occurred. The multivariable adjusted hazard ratios for type 2 diabetes were 1.31 (95% confidence interval 1.19 to 1.44) per five year increment of duration of rotating night shift work and 2.30 (1.88 to 2.83) per unhealthy lifestyle factor (ever smoking, low diet quality, low physical activity, and overweight or obesity). For the joint association of per five year increment rotating night shift work and per unhealthy lifestyle factor with type 2 diabetes, the hazard ratio was 2.83 (2.15 to 3.73) with a significant additive interaction (P for interaction <0.001). The proportions of the joint association were 17.1% (14.0% to 20.8%) for rotating night shift work alone, 71.2% (66.9% to 75.8%) for unhealthy lifestyle alone, and 11.3% (7.3% to 17.3%) for their additive interaction.ConclusionsAmong female nurses, both rotating night shift work and unhealthy lifestyle were associated with a higher risk of type 2 diabetes. The excess risk of rotating night shift work combined with unhealthy lifestyle was higher than the addition of risk associated with each individual factor. These findings suggest that most cases of type 2 diabetes could be prevented by adhering to a healthy lifestyle, and the benefits could be greater in rotating night shift workers.Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

26 keywords...

hide…