title: Prospective cohort studies of bowel movement frequency and laxative use and colorectal cancer incidence in US women and men.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  Bowel movement frequency and laxative use appear not to be associated with colorectal cancer risk in this study.
authors: Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA. poxue@channing.harvard.edu
authors: Xuehong
authors: X
authors: Zhang
authors: Kana
authors: K
authors: Wu
authors: Eunyoung
authors: E
authors: Cho
authors: Jing
authors: J
authors: Ma
authors: Andrew T
authors: AT
authors: Chan
authors: Xiang
authors: X
authors: Gao
authors: Walter C
authors: WC
authors: Willett
authors: Charles S
authors: CS
authors: Fuchs
authors: Edward L
authors: EL
authors: Giovannucci
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D003672:Defecation; D005260:Female; D006801:Humans; D054368:Laxatives / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors
chemical_list: D054368:Laxatives