title: Smoking, alcohol, diabetes, obesity, socioeconomic status, and the risk of colorectal cancer in a population-based case-control study.
abstract: OBJECTIVE
  Although previous research has identified factors that may determine willingness to participate in research, relatively few studies have attempted to quantify the impact non-participation may have on exposure-disease associations. The aims of this study were to (a) investigate the associations between smoking, alcohol, diabetes, obesity, and socioeconomic status and the risk of colorectal cancer in a case-control study (59.7 and 47.2 % response fractions among cases and controls, respectively); and (b) perform sensitivity analyses to examine the possible influence of non-participation.
  
  
  METHODS
  Logistic regression was used to estimate the exposure-disease associations. We then investigated the associations between various demographic and health factors and the likelihood that an individual would participate in the case-control study and then performed two sensitivity analyses (sampling weights and multiple imputation) to examine whether non-participation bias may have influenced the exposure-disease associations.
  
  
  RESULTS
  The exposures alcohol, smoking, and diabetes were associated with an increased risk of colorectal cancer. We found some differences between cases and controls when examining the factors associated with the participation in the study, and in the sensitivity analyses, the exposure-disease associations were slightly attenuated when compared with those from the original analysis.
  
  
  CONCLUSIONS
  Non-participation may have biased the risk estimates away from the null, but generally not enough to change the conclusions of the study.
authors.affiliation: Cancer Control Research, British Columbia Cancer Agency, 675 West 10th Avenue, Vancouver, BC, V5Z 1L3, Canada, tboyle@bccrc.ca.
authors.forename: Terry
authors.initials: T
authors.lastname: Boyle
authors.forename: Lin
authors.initials: L
authors.lastname: Fritschi
authors.forename: Seyed Mehdi
authors.initials: SM
authors.lastname: Tabatabaei
authors.forename: Kathrin
authors.initials: K
authors.lastname: Ringwald
authors.forename: Jane S
authors.initials: JS
authors.lastname: Heyworth
mesh_terms: D000328:Adult; D000368:Aged; D000428:Alcohol Drinking / Q000009:adverse effects / Q000453:epidemiology*; D016022:Case-Control Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000209:etiology; D003920:Diabetes Mellitus / Q000453:epidemiology*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000453:epidemiology*; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology*; D012959:Socioeconomic Factors; D014904:Western Australia / Q000453:epidemiology