Individuals raised on a farm appear to have less asthma than individual raised elsewhere. However, selective migration might contribute to this as may also the suggested protection from farm environment. This study investigated if parents with asthma are less likely to raise their children on a farm. This study involved three generations: 6045 participants in ECRHS/RHINE cohorts (born 1945–1973, denoted G1), their 10,121 parents (denoted G0) and their 8260 offspring participating in RHINESSA (born 1963–1998, denoted G2). G2-offspring provided information on parents not participating in ECRHS/RHINE. Asthma status and place of upbringing for all three generations were reported in questionnaires by G1 in 2010–2012 and by G2 in 2013–2016. Binary regressions with farm upbringing as outcome were performed to explore associations between parental asthma and offspring farm upbringing in G0–G1 and G1–G2. Having at least one parent with asthma was not associated with offspring farm upbringing, either in G1–G2 (RR 1.11, 95% CI 0.81–1.52) or in G0–G1 (RR 0.99, 0.85–1.15). G1 parents with asthma born in a city tended to move and raise their G2 offspring on a farm (RR 2.00, 1.12–3.55), while G1 parents with asthma born on a farm were less likely to raise their G2 offspring on a farm (RR 0.34, 0.11–1.06). This pattern was not observed in analyses of G0–G1. This study suggests that the protective effect from farm upbringing on subsequent asthma development could not be explained by selective migration. Intriguingly, asthmatic parents appeared to change environment when having children.
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The ECRHS/RHINE/RHINESSA study was supported by grants from The Faculty of Health, Aarhus University, Denmark (Project No. 240008), The Wood Dust Foundation (Project No. 444508795), The Danish Lung Association, the Swedish Heart and Lung Foundation, the Swedish Association Against Asthma and Allergy, the Swedish Association against Heart and Lung Disease, the Swedish Council for Working Life and Social Research, The Bror Hjerpstedt Foundation, The Vårdal Foundation for Health Care and Allergic Research, The Norwegian Research Council (Grant Nos. 214123, 230827/F20, 228174 and 135773/330), The Norwegian Asthma and Allergy Association, HelseVest Norway (Grant No. 911 631), The Icelandic Research Council, The University of Iceland Research Fund, The Icelandic GP’s Research Fund, The Estonian Science Foundation (Grant No. 4350), The Estonian Research Council (Grant No. PUT562), Melbourne University, National Health & Medical Research Council of Australia, SEPAR Spain, Sociedad Española de Neumologia y Cirugía Toracica Spain and Horizon2020 PHC1 (Grant No. 633212). For further information about funding sources, please consult www.rhinessa.net. Vivi Schlünssen and Cecilie Svanes are members of the COST BM1201 network. Signe Timm received a PhD scholarship from Aarhus University, Denmark.
Conflict of interest
Michael Abramson has received investigator-initiated grants from Pfizer and Boehringer-Ingelheim for unrelated research. The other authors declare no conflict of interest.
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Timm, S., Frydenberg, M., Abramson, M.J. et al. Asthma and selective migration from farming environments in a three-generation cohort study. Eur J Epidemiol 34, 601–609 (2019). https://doi.org/10.1007/s10654-019-00491-9
- Selective migration