[1] McMaster Univ, Dept Clin Epidemiol & Biostat, Hamilton, ON, Canada
[2] Publ Hlth Serv, Hamilton, ON, Canada
[3] BC Ctr Dis Control, Dept Epidemiol, Vancouver, BC, Canada
[4] Univ British Columbia, Sch Populat & Publ Hlth, Vancouver, BC V5Z 1M9, Canada