[1] Karolinska Inst, Dept Med Epidemiol & Biostat, Stockholm, Sweden
[2] Orebro Univ Hosp, Dept Paediat, Orebro, Sweden
[3] Univ Nottingham, Sch Med, Div Epidemiol & Publ Hlth, Nottingham, England
[4] Columbia Univ, New York, NY 10027 USA
[5] Karolinska Univ Hosp, Inflammat & Infect Theme, Patient Area Gastroenterol Dermatovenerol & Rheum, Stockholm, Sweden
[6] Karolinska Inst, Inst Med Solna, Unit Internal Med, Stockholm, Sweden
[7] Karolinska Inst, Inst Environm Med, Unit Biostat, Stockholm, Sweden
[8] Uppsala Univ, Dept Surg Sci, Uppsala, Sweden
[9] Karolinska Inst, Dept Med Solna, Clin Epidemiol Unit, Stockholm, Sweden
[10] Sachs Children & Youth Hosp, Dept Pediat Gastroenterol & Nutr, Stockholm, Sweden
[11] Karolinska Inst, Sodersjukhuset, Dept Clin Sci & Educ, Stockholm, Sweden