AUTHOR=Dun Aishe , Zhao Xuan , Jin Xu , Wei Tao , Gao Xiang , Wang Youxin , Hou Haifeng 

TITLE=Association Between Night-Shift Work and Cancer Risk: Updated Systematic Review and Meta-Analysis

JOURNAL=Frontiers in Oncology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2020.01006

DOI=10.3389/fonc.2020.01006

ISSN=2234-943X

ABSTRACT=<p><bold>Background:</bold> Nightshift work introduces light at night and causes circadian rhythm among night workers, who are considered to be at increased risk of cancer. However, in the last 2 years, nine population-based studies reported insignificant associations between night-shift work and cancer risks. We aimed to conduct an updated systematic review and meta-analysis to ascertain the effect of night-shift work on the incidence of cancers.</p><p><bold>Methods:</bold> Our protocol was registered in PROSPERO and complied with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Embase, PubMed, and Web of Science databases were used to comprehensively search studies published up to May 31, 2019. The random-effect model (Der Simonian-Laird method) was carried out to combine the risk estimates of night-shift work for cancers. The dose-response meta-analysis was performed to verify whether the association was in a dose-dependent manner.</p><p><bold>Results:</bold> Our literature searching retrieved 1,660 publications. Included in the meta-analyses were 57 eligible studies with 8,477,849 participants (mean age 55 years; 2,560,886 men, 4,220,154 women, and 1,696,809 not mentioned). The pooled results showed that night-shift work was not associated with the risk of breast cancer (<italic>OR</italic> = 1.009, 95% CI = 0.984–1.033), prostate cancer (<italic>OR</italic> = 1.027, 95% CI = 0.982–1.071), ovarian cancer (<italic>OR</italic> = 1.027, 95% CI = 0.942–1.113), pancreatic cancer (<italic>OR</italic> = 1.007, 95% CI = 0.910–1.104), colorectal cancer (<italic>OR</italic> = 1.016, 95% CI = 0.964–1.068), non-Hodgkin's lymph (<italic>OR</italic> = 1.046, 95% CI = 0.994–1.098), and stomach cancer (<italic>OR</italic> = 1.064, 95% CI = 0.971–1.157), while night-shift work was associated with a reduction of lung cancer (<italic>OR</italic> = 0.949, 95% CI = 0.903–0.996), and skin cancer (<italic>OR</italic> = 0.916, 95% CI = 0.879–0.953). The dose-response meta-analysis found that cancer risk was not significantly elevated with the increased light exposure of night- shift work.</p><p><bold>Conclusion:</bold> This systematic review of 57 observational studies did not find an overall association between ever-exposure to night-shift work and the risk of breast, prostate ovarian, pancreatic, colorectal, non-Hodgkin's lymph, and stomach cancers.</p>