Introduction 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 for this association. 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 constipation status, and for case-control studies number of subjects with constipation according to CRC status. Study quality was assessed according to published criteria. Data were pooled using a random effects model, and the association between CRC and constipation was summarised using an odds ratio (OR) with a 95% confidence interval (CI).

Results The search strategy identified 2282 citations, of which 28 were eligible. In eight cross-sectional surveys, presence of constipation as the primary indication for colonoscopywas associated with a lower prevalence of CRC (OR 0.56; 95% CI 0.36–0.89). There was a trend towards 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.

Conclusion Conclusions: 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.

Disclosure of Interest None Declared.