title: Participation bias in postal surveys among older adults: the role played by self-reported health, physical functional decline and frailty.
abstract: Postal survey is a simple and efficient way to collect information in large study samples. The purpose of this study was to find out differences between older adults who responded to a postal survey on health outcomes and those who did not, and to examine the importance of frailty, physical functional decline and poor self-reported health in determining non-response. We mailed out a questionnaire on general health twice at a year's interval to 1000 individuals ≥60 years, and members of the medical insurance scheme of the French national education system. At Year1, 535 persons responded to the questionnaire (65% women, 70.9 ± 8.4 years). A year later (Year2), we obtained 384 responses (63.3% women, 70.5 ± 7.8 years). Compared to respondents, non-respondents at Year2 were more frequently categorized as frail, reported more often to be in bad health, and had more physical functional declines. Frailty, physical functional decline and poor self-reported health increased the likelihood of not responding to Year2 questionnaire, with poor self-reported health weakening the association of physical functional decline and non-response. Respondents of this postal survey are fitter and healthier than non-respondents. This participation bias precludes the generalization of postal surveys results.
authors.affiliation: Aix-Marseille Univ., UMR 7268 Anthropologie Bioculturelle, Droit, Ethique et Santé, France. hilipebarreto81@yahoo.com.br
authors.forename: Philipe de Souto
authors.initials: Pde S
authors.lastname: Barreto
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015982:Bias; D003430:Cross-Sectional Studies; D005260:Female; D016330:Frail Elderly / Q000706:statistics & numerical data*; D005602:France / Q000453:epidemiology; D015577:Geriatric Assessment / Q000706:statistics & numerical data; D006304:Health Status; D006306:Health Surveys / Q000379:methods* / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010809:Physical Fitness; D011177:Postal Service; D011446:Prospective Studies; D057566:Self Report; D011795:Surveys and Questionnaires