[1] London Sch Hyg & Trop Med, Fac Epidemiol & Populat Hlth, London WC1E 7HT, England
[2] Aarhus Univ, Dept Clin Epidemiol, Aarhus, Denmark
[3] Ottawa Hosp, Res Inst, Ottawa, ON, Canada
[4] Univ Ottawa, Sch Epidemiol & Publ Hlth, Ottawa, ON, Canada
[5] McGill Univ, Dept Med, Montreal, PQ, Canada
[6] McGill Univ, Dept Biostat & Occupat Hlth, Montreal, PQ, Canada
[7] Jewish Gen Hosp, Ctr Clin Epidemiol, Lady Davis Inst, Montreal, PQ, Canada
[8] Univ Utrecht, Utrecht Inst Pharmaceut Sci, Div Pharmacoepidemiol & Clin Pharmacol, Utrecht, Netherlands
[9] UCL, Dept Primary Care & Populat Hlth, London, England
[10] Univ Manchester, Manchester Acad Hlth Sci Ctr, Arthrit Res UK Ctr Epidemiol, Div Musculoskeletal & Dermatol Sci,Sch Biol Sci, Manchester, Lancs, England
[11] Inst Clin Evaluat Sci, Toronto, ON, Canada
[12] Univ Toronto, Hosp Sick Children, Dept Paediat, Toronto, ON, Canada
[13] UCL, Great Ormond St Inst Child Hlth, ICH Populat Policy & Practice Programme, London, England
[14] Univ Basel, Univ Basel Hosp, Dept Clin Res, Basel Inst Clin Epidemiol & Biostat, Basel, Switzerland
[15] Brigham & Womens Hosp, Div Pharmacoepidemiol & Pharmacoecon, Dept Med, Boston, MA USA
[16] Harvard Med Sch, Boston, MA USA
[17] Univ Med Ctr Utrecht, Julius Global Hlth, Utrecht, Netherlands
[18] Univ Lausanne, Cochrane Switzerland, Inst Social & Prevent Med, Lausanne, Switzerland
[19] Univ Ottawa, Dept Pediat, Ottawa, ON, Canada
[20] Univ Ottawa, Sch Epidemiol & Publ Hlth, Ottawa, ON, Canada
[21] Childrens Hosp, Eastern Ontario Res Inst, Ottawa, ON, Canada