[1] Vet Affairs Med Ctr, Div Geriatr, San Francisco, CA 94121 USA
[2] Univ Calif San Francisco, San Francisco, CA 94143 USA
[3] Univ N Carolina, Sch Med, Div Gen Med & Clin Epidemiol, Chapel Hill, NC 27515 USA
[4] Harvard Pilgrim Hlth Care, Dept Ambulatory Care & Prevent, Boston, MA USA
[5] Harvard Univ, Sch Med, Boston, MA 02115 USA