A prospective study of the effect of bowel movement frequency, constipation, and laxative use on colorectal cancer risk.

OBJECTIVES

Constipation and laxative use have been hypothesized to increase colorectal cancer (CRC) risk, but existing epidemiologic studies have been inconclusive. To address this issue, the authors prospectively examined the association between CRC incidence and constipation, non-fiber laxative use, and fiber laxative use among 75,214 participants of the VITamins And Lifestyle study.

METHODS

Information on bowel movement frequency as well as average 10-year non-fiber laxative use, fiber laxative use, and constipation was ascertained by means of a questionnaire. Patients were followed from the time of receipt of the baseline questionnaire (2000-2002) until 2008 for CRC incidence, over which time 558 incident CRC cases occurred. Cox proportional hazard models were used to estimate the multivariate-adjusted hazard ratios (HRs) and 95% confidence intervals (95% CI).

RESULTS

Compared with individuals who used non-fiber laxatives less than once per year, the HRs associated with low (1-4 times per year) and high (≥5 times per year) use were 1.49 (95% CI: 1.04-2.14) and 1.43 (95% CI: 0.82-2.28), respectively (Ptrend=0.05). HRs for CRC were statistically significantly decreased and lowest in individuals who reported using fiber laxatives often (4+ days per week for 4+ years) vs. those who reported no use (HR=0.44; 95% CI: 0.21-0.95), although the trend was not significant (Ptrend=0.19). No statistically significant associations between bowel movement frequency or constipation and CRC risk were observed.

CONCLUSIONS

Findings from this study suggest that risk for CRC increases with non-fiber laxative use and decreases with fiber laxative use. However, further observational and experimental studies are needed to clarify these relationships before drawing conclusions about the preferred treatment of constipation.