Purpose: The associations between bowel movement frequency, laxative use, and colorectal cancer incidence remain uncertain. No published studies have accounted for potential latency between these factors and colorectal cancer onset.
Methods: We prospectively examined these associations among 88,173 women in the Nurses' Health Study (NHS, 1982-2010) and 23,722 men in the Health Professionals Follow-up Study (HPFS, 2000-2010). Cox proportional hazards regression models were used to estimate multivariable hazard ratios (HRs, 95 % CIs). We conducted time lagged analyses to evaluate the potential latency in the NHS.
Results: We documented 2,012 incident colorectal cancer cases. The HRs (95 % CIs) for infrequent bowel movement relative to daily were 0.86 (95 % CI 0.71-1.04) in women and 0.81 (95 % CI 0.48-1.37) in men. The HRs for weekly to daily relative to never laxative use were 0.98 (95 % CI 0.81-1.20) in women and 1.41 (95 % CI 0.96-2.06) in men. In women, the HRs for every 3 days or less bowel movement relative to daily were 0.87 (95 % CI 0.59-1.27) for colorectal cancers that developed within 10 years of assessment, 1.03 (95 % CI 0.85-1.26) for 11-18 years after assessment, and 0.73 (95 % CI 0.54-1.01) for 19-28 years after assessment. The corresponding HRs for weekly to daily relative to never laxative use were 0.93 (95 % CI 0.63-1.37), 1.03 (95 % CI 0.74-1.44), and 0.98 (95 % CI 0.71-1.35), respectively.
Conclusion: Bowel movement frequency and laxative use appear not to be associated with colorectal cancer risk in this study.