Does night-shift work increase the risk of prostate cancer? a systematic review and meta-analysis.
BACKGROUND
Night-shift work is suggested to be associated with an increased risk of breast cancer, but its association with prostate cancer is still controversial. We examined this association by conducting a systematic review and meta-analysis.


METHODS
Studies were identified by searching PubMed, EMBASE, Ovid, Web of Science, the Cochrane register, and the China National Knowledge Infrastructure databases through December 25, 2014. Summary relative risks (SRRs) with their corresponding 95% confidence intervals (CIs) were calculated using a random effects or fixed effects model. Heterogeneity and publication bias were also evaluated.


RESULTS
A total of 2,459,845 individuals from eight published studies were included in this meta-analysis. Analysis of all studies suggested that night-shift work was associated with a significantly increased risk of prostate cancer (RR: 1.24, 95% CI: 1.05-1.46; P=0.011). Sensitivity analysis showed that the association remained significant when repeating the analysis after removing one study each time. Dose-response meta-analysis suggested that an increase in night-shift work of 5 years duration was statistically significantly associated with a 2.8% (95% CI: 0.3, 5.4%, P=0.030) increase in the risk of prostate cancer. There was no significant publication bias.


CONCLUSIONS
Based on a meta-analysis, night-shift work is associated with an increased risk of prostate cancer. Because of the limited number of included studies and the large level of heterogeneity, further well-designed studies are still warranted to confirm the findings of our analysis.
Department of Urology, First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, People's Republic of China ; Department of Urology, Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, People's Republic of China.
Dapang
D
Rao
Department of Urology, Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, People's Republic of China.
Haifeng
H
Yu
Department of Urology, Yunnan Tumor Hospital and Third Affiliated Hospital of Kunming Medical University, Kunming, People's Republic of China.
Yu
Y
Bai
Department of Urology, First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, People's Republic of China.
Xiangyi
X
Zheng
Department of Urology, First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, People's Republic of China.
Liping
L
Xie
meta-analysis; prostate cancer; risk; shift work