Association between Sleep Duration and Cancer Risk: A Meta-Analysis of Prospective Cohort Studies

Background: Sleep duration has been shown to play an important role in the development of cancer. However, the results have been inconsistent. A meta-analysis with prospective cohort studies was performed to clarify the association between short or long sleep duration and cancer risk. Methods: PubMed and Embase databases were searched for eligible publications. Pooled relative risk (RR) with 95% confidence interval (CI) was calculated using random-or fixed-model. Results: A total of 10 prospective studies (8392 incident cases and 555678 participants) were included in the meta-analysis. Neither short nor long sleep duration was statistically associated with increased risk of cancer (short sleep duration: RR=1.05, 95% CI=0.90-1.24, p=0.523; long sleep duration: RR=0.92, 95% CI=0.76-1.12, p=0.415). In the subgroup by cancer type, long sleep duration was positively associated with colorectal cancer (RR=1.29, 95% CI=1.09-1.52, p=0.003). Conclusion: The present meta-analysis suggested that neither short nor long sleep duration was significantly associated with risk of cancer, although long sleep duration increased risk of with colorectal cancer. Large-scale well-design prospective studies are required to be conducted to further investigate the observed association.