[1] Univ Calgary, Dept Community Hlth Sci, Calgary, AB T2N 4Z6, Canada
[2] Univ Ottawa, Dept Community Med & Epidemiol, Ottawa, ON, Canada
[3] Ottawa Hosp, Ottawa Hlth Res Inst, Clin Epidemiol Program, Ottawa, ON, Canada
[4] Univ Ottawa, Dept Pediat, Ottawa, ON K1N 6N5, Canada
[5] Eastern Ontario Res Inst, Childrens Hosp, Calgary, AB, Canada