TY - JOUR T1 - A follow-up study of non-responders in a population-based study on respiratory health in Norway JF - European Respiratory Journal JO - Eur Respir J DO - 10.1183/13993003.congress-2015.PA2027 VL - 46 IS - suppl 59 SP - PA2027 AU - Regine Abrahamsen AU - Anne Kristin Møller Fell AU - Paul Henneberger AU - Martin Veel Svendsen AU - Kjell Torèn AU - Johny Kongerud Y1 - 2015/09/01 UR - http://erj.ersjournals.com/content/46/suppl_59/PA2027.abstract N2 - Objectives: Declining participation in epidemiological studies has been reported in recent decades and may lead to biased prevalence estimates. The aim of the study was to identify causes of non-response and the impact on prevalence estimates in a population-based study of respiratory health in Norway.Methods: In 2013, a random sample of 50 000 inhabitants aged 16-50, living in Telemark county received a validated postal questionnaire. The response rate was 33 %. A random sample of 700 non-responders was contacted first by telephone and then by mail.Results: A total of 260 non-responders participated. Non-response was associated with younger age, being male, living in rural area, and past smoking. The prevalence was similar for responders and non-responders for physician diagnosed asthma (12.0% vs 11.5%) and several respiratory symptoms. However, the prevalence of longstanding cough (21.3% vs 15.6%) and use of asthma medication (7.5% vs 3.9%) was greater for responders, and these differences were confirmed when we modelled response and controlled for potential confounders. We weighted the estimates from responders and non-responders based on the proportion of the entire sample each represented to yield adjusted prevalence estimates of 17.4% for longstanding cough and 5.1% for use of asthma medication. The most common self-reported causes for non-response were no reason (28.1%) and forgetting to answer (18.5%).Conclusion: The survey data can directly provide valid estimates of many risk factors and respiratory outcomes, while it was necessary to adjust prevalence estimates for two respiratory symptoms to more accurately represent the sample of eligible individuals. ER -