Andreas A Teferra1,2,3, Judith M Vonk1,2, H Marike Boezen4,2. 1. Department of Epidemiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands. 2. Groningen Research Institute for Asthma and COPD (GRIAC), University of Groningen, University Medical Center Groningen, Groningen, The Netherlands. 3. Division of Epidemiology, College of Public Health, The Ohio State University, Columbus, OH, USA. 4. Department of Epidemiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands h.m.boezen@umcg.nl.