1. Department of Pediatrics; District General Hospital of Førde; Førde Norway
2. Department of Clinical Science, Section for Pediatrics; University of Bergen; Bergen Norway
3. Centre for Clinical Research; Haukeland University Hospital; Bergen Norway
4. Department of Global Public Health and Primary Care, Research Group for Lifestyle Epidemiology; University of Bergen; Bergen Norway
5. Department of Pediatrics; Stavanger University Hospital; Stavanger Norway
6. Environment and Health, Department of Public Health and Primary Care; KU Leuven - University of Leuven; Leuven Belgium
7. Department of Pediatrics; Haukeland University Hospital; Bergen Norway