[1] Kingston Gen Hosp, Dept Med, Kingston, ON K7L 2V7, Canada
[2] Queens Univ, Dept Community Hlth & Epidemiol, Kingston, ON, Canada
[3] Queen Elizabeth 2 Hlth Sci Ctr, Dept Med, Halifax, NS, Canada
[4] Dalhousie Univ, Halifax, NS, Canada
[5] St Pauls Hosp, Program Crit Care Med, Vancouver, BC, Canada
[6] St Pauls Hosp, Ctr Hlth Evaluat & Outcome Sci, Vancouver, BC, Canada
[7] Univ British Columbia, Vancouver, BC V5Z 1M9, Canada
[8] McMaster Univ, Dept Med, Hamilton, ON, Canada
[9] McMaster Univ, Dept Clin Epidemiol, Hamilton, ON, Canada