[1] Univ Bern, Inst Social & Prevent Med, Bern, Switzerland
[2] Univ Bern, Dept Paediat, Div Paediat Resp Med & Allergol, Inselspital, Bern, Switzerland
[3] Univ Zurich, Univ Childrens Hosp Zurich, Dept Resp Med, Zurich, Switzerland
[4] Univ Zurich, Childrens Res Ctr, Zurich, Switzerland
[5] Childrens Hosp Cent Switzerland, Div Paediat Pulmonol, Luzern, Switzerland