title: An investigation into nonresponse bias in a postal survey on urinary symptoms.
abstract: OBJECTIVE
  To investigate nonresponse bias in a postal survey on urinary symptoms in people aged >or= 40 years.
  
  
  METHODS
  Nonresponders to a postal survey on incontinence and other urinary symptoms were studied. A random sample of 1050 nonresponders (stratified for age and sex) was traced by a team of interviewers. Eligible nonresponders were asked several questions from the postal questionnaire, and their reason for not participating in the postal survey.
  
  
  RESULTS
  Only 1% of those not responding were not traced in person or accounted for, and 12% were identified as not eligible to be in the survey sample (moved from address, deceased, residential home). Half of the eligible nonresponders (51%) did not answer the interviewer's questions, the main reason being general unwillingness or disinterest. The number in whom poor health was the reason increased with age. Comparing nonresponders who answered the interviewer's questions with a random sample of responders from the postal survey showed little difference in the reporting of urinary symptoms, although there were differences in general health and long-term health problems. Separate analyses by age showed greater reporting of some urinary symptoms and of poorer general health in the older nonresponders (>or= 70 years).
  
  
  CONCLUSIONS
  Overall, for people aged >or= 40 years there was no evidence of a nonresponse bias in the reporting of urinary symptoms, providing confidence in such prevalence rates. However, poorer general health and greater reporting of some urinary symptoms by the older nonresponders (>or= 70 years) suggests prevalence rates in this age group may be underestimated.
authors.affiliation: Department of Epidemiology and Public Health, University of Leicester, UK. Hmd2@le.ac.uk
authors.forename: H M
authors.initials: HM
authors.lastname: Dallosso
authors.forename: R J
authors.initials: RJ
authors.lastname: Matthews
authors.forename: C W
authors.initials: CW
authors.lastname: McGrother
authors.forename: M
authors.initials: M
authors.lastname: Clarke
authors.forename: S I
authors.initials: SI
authors.lastname: Perry
authors.forename: C
authors.initials: C
authors.lastname: Shaw
authors.forename: C
authors.initials: C
authors.lastname: Jagger
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D015982:Bias; D004739:England / Q000453:epidemiology; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D011177:Postal Service; D017678:Sex Distribution; D011795:Surveys and Questionnaires; D014549:Urinary Incontinence / Q000453:epidemiology; D014570:Urologic Diseases / Q000453:epidemiology*