[1] Lund Univ, Dept Pediat, Skane Univ Hosp, Malmo, Sweden
[2] Univ S Florida, Pediat Epidemiol Ctr, Tampa, FL USA
[3] Wake Forest Univ, Dept Epidemiol, Winston Salem, NC 27109 USA
[4] Colorado Sch Publ Hlth, Dept Epidemiol, Aurora, CO USA
[5] Univ Cincinnati, Dept Pediat, Cincinnati, OH 45221 USA
[6] Univ Washington, Dept Pediat, Seattle, WA 98195 USA
[7] Univ Helsinki, Childrens Hosp, Helsinki, Finland
[8] Univ Helsinki, Cent Hosp, Helsinki, Finland
[9] Folkhalsan Res Ctr, Helsinki, Finland
[10] Tampere Univ Hosp, Dept Pediat, Tampere, Finland
[11] Univ Oulu, Dept Pediat, SF-90100 Oulu, Finland
[12] Univ Gothenburg, Dept Pediat, Sahlgrenska Acad, Gothenburg, Sweden
[13] Linkoping Univ, Dept Hlth & Environm, Linkoping, Sweden
[14] Univ Ulm, Inst Epidemiol, Ulm, Germany
[15] Univ Florida, Dept Pediat, Gainesville, FL USA