Laxative type in relation to colorectal cancer risk.

Purpose: Existing studies on laxatives, used by roughly 40% of the U.S. population experiencing constipation and colorectal cancer (CRC) have yielded inconsistent results, which may be due to a failure to account for differential risks by major laxative types: bulk (fiber-based), and nonbulk (or nonfiber-based).

Methods: We examined the association of nonfiber-based laxative use and fiber-based laxative use with the risk of CRC in a subset of the multisite, International Colon Cancer Family Registry cohort comprising 4930 primary invasive CRC cases and 4025 controls selected from the general population. Epidemiologic risk factor questionnaires were administered to all participants at recruitment, and exposures were ascertained approximately 1 year before diagnosis for cases and at a comparable period for controls. We ascertained known and suspected CRC risk factors, including regular laxative use, which was defined as laxative intake at least twice a week for more than a month. Multivariable logistic regression models were used to estimate the adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs).

Results: Individuals who reported using nonfiber-based laxatives regularly were at a significantly increased risk for CRC compared with those who reported no laxative use (OR = 2.17, 95% CI = 1.47-3.19). No statistically significant associations were observed between fiber-based laxative use and CRC (OR = 0.99, 95% CI = 0.80-1.22).

Conclusions: Compared with nonusers, the risk of CRC increased with nonfiber-based laxative use, whereas CRC risk was not significantly associated with fiber-based laxative use.