Abstract 2178: Rotating night shift work and cancer mortality in the nurses' health study

Abstract

Abstract Rotating night-shift work is common in western societies, but epidemiological studies on shift work and cancer mortality are limited. In a prospective closed cohort of 74,914 registered US nurses, the Nurses' Health Study, we examined the impact of rotating night-shift work on total-cancer and cancer-specific mortality. Rotating night-shift work was defined as having worked at least 3 nights per month. Cox proportional hazards models adjusting for age, smoking, BMI, and other important confounders, were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). During 22 years of follow-up, we documented 5,123 cancer deaths. Overall, we observed no association between rotating night-shift work and total-cancer mortality (HR15+years=1.07; 95% CI, 0.97-1.19; Ptrend=0.17). However, women with 15 or more years of night-shift work had a significant increase in lung cancer mortality (multivariable HR=1.25; 95% CI, 1.04-1.50) and a borderline significant increase in colorectal cancer mortality (MV HR=1.32; 95% CI, 0.97-1.81). The increase in lung cancer mortality was limited to current smokers. We observed no increase in breast cancer mortality (HR15+years=1.03; 95%CI, 0.76-1.38; Ptrend=0.97). For cancers with fewer than 200 deaths, we observed a non-significant increase in mortality from kidney cancer, myeloma and leukemia among women with 6-14 and 15+ years of rotating night-shift work: the HRs were 1.58 (95% CI, 0.92-2.71) and 1.36 (95% CI, 0.72-2.56) for kidney cancer, 1.66 (95% CI, 0.98-2.81) and 1.47 (95% CI, 0.79-2.77) for myeloma, 1.25 (95% CI, 0.70-2.23) and 1.53 (95% CI, 0.83-2.83) for leukemia, respectively. We conclude that after adjusting for important confounders, the impact of rotating night-shift work on cancer mortality appears modest. Women working rotating night-shifts for more than 15 years had modestly increased colorectal and lung cancer mortality but the increase in lung cancer mortality was largely limited to current smokers and it is possible that these observations remain residually confounded by smoking. Additional studies are warranted to confirm our findings. Citation Format: Fangyi Gu, Jiali Han, Sue Hankinson, Eva Schernhammer, Nurses' Health Study Group. Rotating night shift work and cancer mortality in the nurses' health study. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2178. doi:10.1158/1538-7445.AM2014-2178