Cristina Ardura-Garcia1, Claudia E Kuehni2,3. 1. Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland. 2. Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland claudia.kuehni@ispm.unibe.ch. 3. Paediatric Respiratory Medicine, Children's University Hospital of Bern, University of Bern, Bern, Switzerland.