title: Interviewer effects when investigating abuse were not compatible with effect modification but instead with confounding.
abstract: OBJECTIVE
  To describe interviewer-related variability in abuse estimates and assess the nature of the interviewer effects on the associations between elder abuse and covariates.
  
  
  METHODS
  After intensive training, six interviewers administered structured questionnaires through face-to-face interviews to assess abuse in a population-based sample of 641 Portuguese individuals aged 60-84 years.
  
  
  RESULTS
  The overall prevalence of abuse victimization during the previous year was 28.1%, but it differed significantly according to the interviewer, ranging from 16.9% to 36.8%. There was no statistical effect modification introduced by the interviewer on the association of abuse and its determinants. Additionally, interviewer-level variables (empathy and violence beliefs) showed no significant contribution to explain the variance attributable to potential interviewer effects. Adjusting for the interviewer had little or no effect on the odds ratio of abuse for gender, age, education, and quality of life. However, the interviewer introduced relevant confounding of the associations between abuse and other sensitive topics, such as somatic complaints.
  
  
  CONCLUSIONS
  Although no relevant effect modification was observed, this study emphasizes the importance of the interviewer as a relevant confounder when estimating associations between sensitive variables, as it is the case of elder abuse.
authors: Department of Clinical Epidemiology, Predictive Medicine and Public Health, University of Porto Medical School, Al. Prof. Hernâni Monteiro, 4200-319 Porto, Portugal. silfraga@med.up.pt
authors: Sílvia
authors: S
authors: Fraga
authors: Raquel
authors: R
authors: Lucas
authors: Diogo
authors: D
authors: Costa
authors: Henrique
authors: H
authors: Barros
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019548:Crime Victims / Q000523:psychology / Q000706:statistics & numerical data*; D030881:Disclosure; D004552:Elder Abuse / Q000523:psychology / Q000706:statistics & numerical data*; D015981:Epidemiologic Factors; D005260:Female; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D011174:Portugal / Q000453:epidemiology; D015995:Prevalence; D012108:Research Personnel / Q000523:psychology; D035844:Researcher-Subject Relations