[1] Heidelberg Univ, Med Fac Mannheim, Mannheim Inst Publ Hlth Social & Prevent Med, Univ Med Mannheim, D-68167 Mannheim, Germany
[2] Heidelberg Univ, Univ Med Mannheim, Childrens Hosp, D-68167 Mannheim, Germany
[3] Case Western Reserve Univ, Dept Med, Cleveland, OH 44106 USA
[4] Case Western Reserve Univ, Dept Epidemiol, Cleveland, OH 44106 USA
[5] Case Western Reserve Univ, Dept Biostat, Cleveland, OH 44106 USA
[6] Res Ctr Phys Educ & Sports Children & Adolescents, Karlsruhe, Germany