[1] Charite, Dept Paediat Pneumol & Immunol, D-13353 Berlin, Germany
[2] Laltrastatistics Srl, Consultancy & Training Biostat Off, Rome, Italy
[3] Tech Univ Munich, Dept Pediat, D-80290 Munich, Germany
[4] St Josefs Hosp, Dept Pediat, Freiburg, Germany
[5] Johannes Gutenberg Univ Med Ctr, Dept Pediat & Adolescent Med, Mainz, Germany
[6] Univ Dusseldorf, Dept Pediat Cardiol & Pneumol, Dusseldorf, Germany
[7] Charite, Inst Social Med Epidemiol & Hlth Econ, D-13353 Berlin, Germany
[8] Univ Wurzburg, Inst Clin Epidemiol & Biometry, D-97070 Wurzburg, Germany