[1] Ctr Hosp Affilie Univ Quebec, Unite Rech Sante Populat, Quebec City, PQ, Canada
[2] Univ Laval, Dept Med Sociale & Prevent, Quebec City, PQ, Canada
[3] Duke Univ, Med Ctr, Dept Med, Ctr Study Aging & Human Dev,Div Geriatr, Durham, NC 27706 USA
[4] Durham VA Med Ctr, Geriatr Res Educ & Clin Ctr, Durham, NC USA
[5] Univ Colorado, Dept Pediat & Med, Denver, CO 80202 USA
[6] Hlth Sci Ctr, Aurora, CO USA
[7] Univ Bristol, Bristol, Avon, England
[8] Bristol Royal Infirm & Gen Hosp, Bristol, Avon, England
[9] Univ Calif San Diego, Dept Pathol & Med, La Jolla, CA 92093 USA
[10] San Diego VA Med Ctr, La Jolla, CA USA
[11] Univ British Columbia, Dept Med, Vancouver, BC, Canada
[12] BC Ctr Dis Control, Vancouver, BC, Canada