e15600 Background: Globally, more than 1.8 million people were diagnosed of colorectal cancer (CRC) in 2018, with over 30% of CRC in the rectum. Shift-work, involving circadian disruption, sleep deprivation and lifestyle changes, was designated as a probable cause of cancer by The International Agency for Research on Cancer. Previous studies investigating the impact of permanent night-shift work and rotating shift-work on rectal cancer risk showed controversial results. Thus, this meta-analysis was conducted. Methods: A comprehensive literature search on PubMed was conducted to identify all relevant studies published prior to January 2021 according to the established inclusion criteria. The quality assessment was performed by the Newcastle-Ottawa Scale (NOS). The pooled odds ratio (OR) and 95% confidence intervals (CI) were calculated to estimate the association between the shift-work and rectal cancer risk. Based on heterogeneity significance, random-effect or fixed-effect model was used. Subgroup analyses were conducted to explore the night-shift and rotating-shift, respectively. Sensitivity analysis and publication bias detection were performed, and trim and fill analysis was also conducted. All statistical analyses were performed using RevMan software (version 5.3; Cochrane library) and STATA 15.0 statistical software (Stata Corp., College Station, TX), and all P values were two-tailed, the test level was 0.05. Results: Thirty-seven articles were obtained from database searching. Three articles involving 1,063 rectal cancer cases were included. All studies were considered moderate to high quality. All included studies investigated on the association between shift-work and rectal cancer risk. A statistically significant association between shift-work and increased rectal cancer risk was found (OR 1.53, 95%CI: 1.31, 1.79, P< 0.00001, I 2 = 35%). In subgroup analyses, night-shift work was associated with a non-statistically significant increased risk of rectal cancer (OR 1.25, 95%CI: 0.47, 3.32, P = 0.66, I 2 = 93%). In contrast, Rotating-shift was associated with a statistically significant increased rectal cancer risk (OR 1.35, 95%CI: 1.10, 1.65, P = 0.004, I 2 = 6%). Sensitivity analysis confirmed the stability of the result. Funnel plot, Egger's test (t = 1.69, P = 0.341), and Begg's test (z = 1.04, P = 0.296) found no publication bias of analysis. Trim and fill analysis on fixed-effect model showed the pooled OR kept stable after adding two “missing” studies (OR 1.403, 95%CI: 1.224, 1.609, P <0.05). Conclusions: The current meta-analysis demonstrates that shift-work is associated with increased rectal cancer risk. However, no association between night-shift work and rectal cancer risk was found. In contrast, association between rotating-shift work and increased rectal cancer risk was found. More original studies on this topic are needed to further explore shift-work impacts on rectal cancer risk.
Shift Work and Breast Cancer
