1. Institute of Social and Preventive MedicineUniversity of BernBernSwitzerland
2. Oslo Centre for Biostatistics and EpidemiologyOslo University Hospital and Department of BiostatisticsInstitute of Basic Medical SciencesUniversity of OsloOsloNorway
3. Department of PediatricsRespiratory UnitUniversity of BernBernSwitzerland
4. Division of Human GeneticsUniversity Children's Hospital BernBernSwitzerland
5. Division of Respiratory MedicineUniversity Children's Hospital of ZurichZurichSwitzerland
6. Division of Pediatric PulmonologyChildren's Hospital of Eastern SwitzerlandSt. GallenSwitzerland