Prospective Cohort Study of the Risk of Prostate Cancer among Rotating-Shift Workers: Findings from the Japan Collaborative Cohort Study

TLDR

Shift work has been linked to increased risk of several cancers, but its association with prostate cancer had not been previously examined. The study prospectively investigated whether rotating‑shift work is associated with prostate cancer incidence among 14,052 Japanese men. Baseline data collected 1988‑1990 classified participants by day, rotating‑shift, or fixed‑night work, and Cox proportional hazards models adjusted for demographic, lifestyle, and occupational factors estimated relative risks. During 111,974 person‑years, 31 prostate cancers were diagnosed, and rotating‑shift workers had a significantly higher risk (RR = 3.0, 95 % CI 1.2–7.7) compared with day workers, while fixed‑night work showed only a small, nonsignificant increase, marking the first evidence of a link between rotating shift work and prostate cancer.

Abstract

Shift workers have been reported to have an increased risk of some cancers. However, the risk of prostate cancer in shift workers is not known to have been examined previously. This study prospectively examined the association between shift work and risk of prostate cancer incidence among 14,052 working men in Japan enrolled in a large-scale prospective cohort. A baseline survey was conducted between 1988 and 1990. Subjects were asked to indicate the most regular work schedule they had undertaken previously: day work, rotating-shift work, or fixed-night work. During 111,974 person-years, 31 cases of prostate cancer were recorded. The Cox proportional hazards model was used to estimate the risk, with adjustments for age, family history of prostate cancer, study area surveyed, body mass index, smoking, alcohol drinking, job type, physical activity at work, workplace, perceived stress, educational level, and marriage status. Compared with day workers, rotating-shift workers were significantly at risk for prostate cancer (relative risk = 3.0, 95% confidence interval: 1.2, 7.7), whereas fixed-night work was associated with a small and nonsignificant increase in risk. This report is the first known to reveal a significant relation between rotating-shift work and prostate cancer.