title: Multiple imputation to account for missing data in a survey: estimating the prevalence of osteoporosis.
abstract: BACKGROUND
  Nonresponse bias is a concern in any epidemiologic survey in which a subset of selected individuals declines to participate.
  
  
  METHODS
  We reviewed multiple imputation, a widely applicable and easy to implement Bayesian methodology to adjust for nonresponse bias. To illustrate the method, we used data from the Canadian Multicentre Osteoporosis Study, a large cohort study of 9423 randomly selected Canadians, designed in part to estimate the prevalence of osteoporosis. Although subjects were randomly selected, only 42% of individuals who were contacted agreed to participate fully in the study. The study design included a brief questionnaire for those invitees who declined further participation in order to collect information on the major risk factors for osteoporosis. These risk factors (which included age, sex, previous fractures, family history of osteoporosis, and current smoking status) were then used to estimate the missing osteoporosis status for nonparticipants using multiple imputation. Both ignorable and nonignorable imputation models are considered.
  
  
  RESULTS
  Our results suggest that selection bias in the study is of concern, but only slightly, in very elderly (age 80+ years), both women and men.
  
  
  CONCLUSIONS
  Epidemiologists should consider using multiple imputation more often than is current practice.
authors.affiliation: Department of Epidemiology, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Quebec H3G 1A4, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Kmetic
authors.forename: Lawrence
authors.initials: L
authors.lastname: Joseph
authors.forename: Claudie
authors.initials: C
authors.lastname: Berger
authors.forename: Alan
authors.initials: A
authors.lastname: Tenenhouse
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001499:Bayes Theorem; D015982:Bias; D002170:Canada / Q000453:epidemiology; D015331:Cohort Studies; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000453:epidemiology*; D015995:Prevalence; D012307:Risk Factors; D011795:Surveys and Questionnaires