title: Colorectal cancer after start of nonsteroidal anti-inflammatory drug use.
abstract: OBJECTIVE
  Nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin, have been consistently shown to reduce the risk of colorectal cancer (CRC) in non-experimental studies, but little is known of the factors associated with starting and continuing regular NSAID use and their effect on the NSAID and CRC association.
  
  
  METHODS
  We performed a prospective cohort study of 22,071 healthy male physicians aged 40 to 84 years without indications or contraindications to regular NSAID use at baseline. Annual questionnaires assessed quantity of NSAID use, occurrence of cancer, and risk factors for CRC. Propensity for regular NSAID use (>60 days/year) was estimated using generalized estimating equations. We used a time-varying Cox proportional hazards model to estimate the association between duration since initiation of regular NSAID use and risk for CRC.
  
  
  RESULTS
  Regular non-aspirin and any NSAID use increased from 0% to 12% and 1% to 56% over time, respectively and was predicted by age, body mass index, alcohol consumption, medication use, coronary artery disease, gastrointestinal diseases, arthritis, hypertension, and headaches. Over a median follow-up of 18 years, 495 physicians were diagnosed with CRC. There was no trend of CRC risk with increased duration of regular NSAID use. Five or more years of regular use of any NSAID were associated with a relative risk for CRC of 1.0 (95% confidence interval: 0.7-1.5), after adjustment for predictors of regular NSAID use.
  
  
  CONCLUSIONS
  Regular NSAID use was not associated with a substantial risk reduction of CRC after controlling for time-varying predictors of both NSAID use and CRC.
authors.affiliation: Division of Preventive Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Mass 02215, USA. til.sturmer@post.harvard.edu
authors.forename: Til
authors.initials: T
authors.lastname: Stürmer
authors.forename: Julie E
authors.initials: JE
authors.lastname: Buring
authors.forename: I-Min
authors.initials: IM
authors.lastname: Lee
authors.forename: Tobias
authors.initials: T
authors.lastname: Kurth
authors.forename: J Michael
authors.initials: JM
authors.lastname: Gaziano
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Glynn
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage*; D001241:Aspirin / Q000008:administration & dosage*; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000517:prevention & control*; D015897:Comorbidity; D015986:Confounding Factors, Epidemiologic; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010820:Physicians / Q000706:statistics & numerical data; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D015983:Selection Bias; D012651:Self Medication; D011795:Surveys and Questionnaires; D013997:Time Factors; D014481:United States / Q000453:epidemiology
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D001241:Aspirin