[1] Royal Victoria Hosp, Dept Clin Epidemiol, Montreal, PQ H3A 1A1, Canada
[2] Univ Toronto, Appl Res Unit, Baycrest Ctr Geriatr Care, Dept Hlth Policy Management & Evaluat, Toronto, ON M6A 2E1, Canada
[3] Univ Washington, Dept Neurol, Seattle, WA 98195 USA