Chronic Constipation as a Risk Factor for Colorectal Cancer: Results From a Nationwide, Case-Control Study

BACKGROUND & AIMS: Prolonged colon transit times may increase the contact time between potential carcinogens in the stool and the colonic mucosa. Nonetheless, previous studies have yielded conflicting results connecting chronic constipation with the risk of colorectal cancer (CRC). We examined the association between chronic constipation and later CRC. METHODS: In this nationwide case-control study, we identified 41,299 CRC cases by colorectal biopsy in Sweden between July 2007 and December 2016 and matched them to 203,181 age- and sexmatched controls from the general population. We compared odds of earlier chronic constipation (defined as >= 2 laxative prescriptions in the Prescribed Drug Register with >= 6 months between the first and last prescription) between CRC cases and controls using logistic regression. In separate analyses, we compared odds of earlier constipation between CRC cases and sibling comparators, but also examined earlier risk of having an inpatient/outpatient specialty diagnosis of chronic constipation before CRC. RESULTS: Overall, 3943 patients with CRC met our criteria for chronic constipation before CRC. The crude proportion of chronic constipation in CRC patients was 9.5% compared with 8.8% in controls. After multivariable adjustment, there was a modest association between chronic constipation and later CRC (odds ratio [OR], 1.10; 95% CI, 1.06-1.14) that vanished using sibling comparators to control for residual confounding (OR, 1.04; 95% CI, 0.97-1.13). In a sensitivity analysis of 126,650 CRC patients diagnosed from 1989 to 2016, we found no association with earlier chronic constipation diagnosed in inpatient/outpatient specialty clinics (OR, 0.88; 95% CI, 0.75-1.04). CONCLUSIONS: In a nationwide case-control study, chronic constipation was not associated with later CRC.