Abstract
BACKGROUND: Although studies have reported that certain sleep characteristics, such as sleep duration and sleep apnea, are linked to the risk of colorectal cancer (CRC), this link remains contentious because of the limited evidence from individual studies. Furthermore, evidence indicated that shift work involving circadian disruption as a probable human carcinogen. This systematic review and meta-analysis aimed to examine the associations between sleep duration, sleep apnea, and shift work with the risk of colorectal neoplasms, including CRC and colorectal adenoma (CRA). METHODS: We conducted a comprehensive literature search in PubMed, Embase, and Web of Science databases. The inclusion criteria were determined using PICOS principles. Observational studies reporting associations of sleep duration, sleep apnea, or shift work with risk of CRC or CRA were included. We assessed the risk of bias on the basis of the Newcastle-Ottawa Scale. RESULTS: A total of 18 observational studies were included. Of these studies, nine studies reported the effect of sleep duration on risk of colorectal neoplasms, five reported the effect of sleep apnea, and six reported the effect of shift work. The relative risk (RR) for colorectal neoplasms was 1.06 [95% confidence interval (CI): 0.94, 1.20] in the short sleep duration group compared with the moderate sleep duration group. Long sleep duration was associated with an increased risk of colorectal neoplasms (RR: 1.33, 95% CI: 1.07, 1.65). The pooled results showed that sleep apnea was associated with an increased risk of colorectal neoplasms (RR: 1.75, 95% CI: 1.56, 1.97). Furthermore, results showed that the association between shift work and the risk of colorectal neoplasms was not significant (RR: 1.06, 95% CI: 0.95, 1.17). No publication bias was observed in all the analyses (all P>0.05). The sensitivity analysis showed that no individual study substantially influenced the pooled RRs for colorectal neoplasms and CRC. CONCLUSIONS: Our findings suggest the significant positive association of long sleep duration and sleep apnea with risk of colorectal neoplasms and CRC. Given that sleep characteristics may be a potentially modifiable risk factor for colorectal neoplasms, further understanding of its role in carcinogenesis will provide valuable insight for cancer prevention.