1. Institut d’Investigacions Biomediques August Pi i Sunyer (IDIBAPS)Barcelona, Spain
2. Centro de Investigación Biomédica en Red de Enfermedades Respiratorias (CIBER)Barcelona, Spain
3. Department of EpidemiologyUniversity of Groningen, University Medical Center GroningenGroningen, the Netherlands
4. Groningen Research Institute for Asthma and COPD (GRIAC)University of Groningen, University Medical Center GroningenGroningen, the Netherlands
5. University of BarcelonaBarcelona, Spain
6. Hospital ClinicBarcelona, Spain