title: Colorectal cancer mortality reduction is associated with having at least 1 colonoscopy within the previous 10 years among a population-wide cohort of screening age.
abstract: OBJECTIVE
  Colonoscopy has been demonstrated to be effective in colorectal cancer (CRC) mortality reduction, although current screening guidelines have yet to be evaluated. We assessed the protective benefit of colonoscopy within the previous 10 years and whether this effect is maintained with age.
  
  
  METHODS
  We used administrative data to compare risk of CRC death (CCD) across colonoscopy utilization among a population-wide cohort comprising individuals aged 60 to 80 years (N = 1,509,423). Baseline and time-dependent colonoscopy exposure models were assessed in the context of competing "other causes of death" (OCDs). Cumulative incidence of CCD and OCD across colonoscopy exposure, over follow-up, was estimated. Relative hazards were computed by age strata (60-69 years, 70-74 years, 75+ years) and proximal and distal cancer subsites.
  
  
  RESULTS
  At least 1 colonoscopy during 10 years before baseline was estimated to provide a 51% reduced hazard of CCD (hazard ratio [HR] 0.49; 95% confidence interval [CI], 0.45-0.54) over the following 8 years. When colonoscopy was modeled as a time-dependent covariate, the risk of CCD was further diminished (multivariable-adjusted HR 0.36; 95% CI, 0.33-0.38). Stratified analyses suggested moderately attenuated CCD risk reduction among the oldest age group; however, consideration of OCDs suggest that this is related to competing risks. CCD risk reduction related to colonoscopy was lower for proximal cancers.
  
  
  CONCLUSIONS
  Colonoscopy within the previous 10 years provides substantial protective benefit for average-risk individuals over 60 years. CCD risk reduction may be maintained well beyond 74 years, a common upper age limit recommended by screening guidelines.
authors.affiliation: Sunnybrook Research Institute, Toronto, Ontario, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Stock
authors.affiliation: Sunnybrook Research Institute, Toronto, Ontario, Canada; Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada; Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada; Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Lawrence F
authors.initials: LF
authors.lastname: Paszat
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada; Cancer Care Ontario, Toronto, Ontario, Canada; Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada; Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Linda
authors.initials: L
authors.lastname: Rabeneck
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002423:Cause of Death; D015331:Cohort Studies; D003113:Colonoscopy / Q000706:statistics & numerical data*; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000401:mortality*; D055088:Early Detection of Cancer / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009026:Mortality; D016016:Proportional Hazards Models