[1] Karolinska Univ Hosp, Astrid Lindgren Childrens Hosp, Dept Womens & Childrens Hlth, Karolinska Inst, S-17176 Stockholm, Sweden
[2] Karolinska Univ Hosp, Karolinska Inst, Dept Oncol Pathol, Karolinska Inst, S-17176 Stockholm, Sweden
[3] Karolinska Univ Hosp, Karolinska Inst, Dept Med, Karolinska Inst, S-17176 Stockholm, Sweden
[4] Karolinska Inst, Clin Epidemiol Unit, Dept Med, Stockholm, Sweden
[5] Orebro Univ Hosp, Clin Epidemiol & Biostat, Orebro, Sweden
[6] Univ Orebro, SE-70182 Orebro, Sweden
[7] UCL, Dept Epidemiol & Publ Hlth, London, England