1. Department of Respiratory Medicine, Bispebjerg Hospital, 2400 Copenhagen, Denmark
2. Danish Epidemiology Science Centre, Statens Serum Institut, 2300 Copenhagen, Denmark
3. Institute of Regional Health Services Research & Odense Patient Data Explorative Network, University of Southern Denmark, 5000 Odense, Denmark
4. The Danish Twin Registry, University of Southern Denmark, 5000 Odense, Denmark
5. Danish Pediatric Asthma Center, Gentofte Hospital, 2900 Hellerup, Denmark
6. Department of Dermato-Allergology, Gentofte Hospital, 2900 Hellerup, Denmark