Association Between Constipation and Colorectal Cancer: Systematic Review and Meta-Analysis of Observational Studies

OBJECTIVES: Constipation is common in the community, and may affect survival adversely. An association between constipation and development of colorectal cancer (CRC) could be one possible explanation. We performed a systematic review and meta- analysis examining this issue. METHODS: We searched MEDLINE, EMBASE, and EMBASE Classic (through July 2012). Eligible studies were cross-sectional surveys, cohort studies, or case-control studies reporting the association between constipation and CRC. For cross- sectional surveys and cohort studies, we recorded number of subjects with CRC according to the constipation status, and for case-control studies, number of subjects with constipation according to CRC status were recorded. Study quality was assessed according to published criteria. Data were pooled using a random effects model, and the association between CRC and constipation was summarized using an odds ratio (OR) with a 95 % confi dence interval (CI). RESULTS: The search strategy identifi ed 2,282 citations, of which 28 were eligible. In eight cross- sectional surveys, presence of constipation as the primary indication for colonoscopy was associated with a lower prevalence of CRC (OR = 0.56; 95 % CI 0.36 - 0.89). There was a trend toward a reduction in odds of CRC in constipation in three cohort studies (OR = 0.80; 95 % CI 0.61 - 1.04). The prevalence of constipation in CRC was signifi cantly higher than in controls without CRC in 17 case-control studies (OR = 1.68; 95 % CI 1.29 - 2.18), but with signifi cant heterogeneity, and possible publication bias. CONCLUSIONS: Prospective cross- sectional surveys and cohort studies demonstrate no increase in prevalence of CRC in patients or individuals with constipation. The signifi cant association observed in case - control studies may relate to recall bias.