1. Institute of Epidemiology and Medical Biometry; Ulm University; Ulm; Germany
2. Department of Child and Adolescent Psychiatry and Psychotherapy; Ulm University; Ulm; Germany
3. Pediatric Respiratory and Allergy Units; “Arrixaca” University Children's Hospital; University of Murcia; CIBER of Epidemiology and Public Health (CIBERSP); Murcia; Spain
4. Pediatrics Department; Torrecardenas Hospital; Almeria; Spain
5. Pediatric Allergy and Pulmonology Units; Pediatrics Department; 12 de Octubre Children's University Hospital; Madrid; Spain
6. Unit of Public Health and Environmental Care; Department of Preventive Medicine; University of Valencia; Research group CIBER CB06/02/0045 CIBER actions-Epidemiology and Public Health; Research Foundation; University Hospital Dr. Peset; Valencia; Spain
7. Division of Community Health Sciences; St George's; University of London; London; UK