Journal Article

Contribution of Follow-up of Nonresponders to Prevalence and Risk Estimates: A Norwegian Respiratory Health Survey

Jan Brøgger, Per Bakke, Geir E. Eide and Amund Gulsvik

in American Journal of Epidemiology

Published on behalf of Johns Hopkins Bloomberg School of Public Health

Volume 157, issue 6, pages 558-566
Published in print March 2003 | ISSN: 0002-9262
Published online March 2003 | e-ISSN: 1476-6256 | DOI:
Contribution of Follow-up of Nonresponders to Prevalence and Risk Estimates: A Norwegian Respiratory Health Survey

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Achieving a high response rate is often expensive and time consuming. Does an extensive survey effort change prevalence estimates and exposure-disease relations? In 1998–1999, the authors conducted a population-based respiratory health survey in two Norwegian counties (Oslo, n = 20,000; Hordaland, n = 5,000) of a random sample of the adult population aged 15–70 years. A postal questionnaire was mailed, with as many as two reminder letters. A 25% random sample of postal nonresponders was contacted by ordinary or cellular telephone. Cumulative response rates after the first mailing, first reminder, second reminder, and telephone follow-up were 42.7%, 60.7%, 68.3%, and 79.9%, respectively. Compared with initial postal responders, responders at later stages were younger, and more were male. Late responders had a lower educational level, were more often smokers, and were occupationally exposed to dusts or gases more frequently. After the authors adjusted for these factors, late responders were found to have less asthma, attacks of breathlessness, and hay fever. Hardly any changes in prevalences and odds ratios were noted when initial responders were compared with all responders. The additional contribution of sending reminder letters and conducting a telephone follow-up to prevalence estimates and the exposure-disease relation was small. A single letter would have produced nearly the same prevalence estimates and risk factor associations.

Keywords: asthma; data collection; epidemiologic methods; health care; interviews; postal service; questionnaires; signs and symptoms, respiratory

Journal Article.  6874 words.  Illustrated.

Subjects: Public Health and Epidemiology

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