Bowel Movement, State of Stool, and Subsequent Risk for Colorectal Cancer: The Japan Public Health Center–Based Prospective Study

Purpose Evidence about whether irregular bowel movements or unusual stool conditions are associated with colorectal cancer is still inconsistent. Methods We identified 479 newly diagnosed cases of colorectal cancer (303 men and 176 women) during a 7.9-year follow-up of a cohort consisting of 57,940 subjects (27,529 men and 30,411 women) aged 40 to 69 years at baseline. Bowel movements and stool conditions were asked through a self-administered questionnaire. Results Neither high nor low frequency of bowel movements was associated with colorectal cancer incidence compared with one bowel movement per day. Multivariate hazard ratios (HRs) and 95% confidence intervals (CIs) for two bowel movements or more per day were 1.03 (95% CI, 0.76–1.41) in men and 1.16 (95% CI, 0.68–2.00) in women. HRs for two to three bowel movements per week were 0.97 (95% CI, 0.61–1.55) in men and 0.75 (95% CI, 0.49–1.13) in women. There was no clear association between an unusual stool state, such as diarrhea or hard stools, and colorectal cancer. Conclusion Our results suggest that neither bowel movement frequency nor any specific state of stool causes colorectal cancer.