1. Department of Pediatric Pulmonology and Pediatric Allergology University Medical Center Groningen Beatrix Children's Hospital University of Groningen Groningen The Netherlands
2. University Medical Center Groningen Groningen Research Institute for Asthma and COPD (GRIAC) University of Groningen Groningen The Netherlands
3. The Netherlands Institute for Risk Assessment Sciences Utrecht University Utrecht The Netherlands
4. Department of Epidemiology University Medical Center Groningen University of Groningen Groningen The Netherlands