[1] Dept Vet Affairs Med Ctr, San Francisco, CA 94121 USA
[2] Univ Calif San Francisco, Dept Med, San Francisco, CA 94143 USA
[3] Univ Calif San Francisco, Dept Epidemiol, San Francisco, CA 94143 USA
[4] Univ Pittsburgh, Dept Epidemiol, Grad Sch Publ Hlth, Pittsburgh, PA 15261 USA
[5] Oregon Hlth & Sci Univ, Div Gen Internal Med & Geriatr, Portland, OR USA
[6] Univ Pittsburgh, Sch Med, Dept Family Med & Clin Epidemiol, Pittsburgh, PA USA