Association between constipation and colorectal cancer: systematic review and meta-analysis of observational studies

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.

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% confidence interval (CI).

The search strategy identified 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 significantly higher than in controls without CRC in 17 case-control studies (OR=1.68; 95% CI 1.29-2.18), but with significant heterogeneity, and possible publication bias.

Prospective cross-sectional surveys and cohort studies demonstrate no increase in prevalence of CRC in patients or individuals with constipation. The significant association observed in case-control studies may relate to recall bias.