[1] Vet Affairs Med Ctr, Ctr Geriatr Res Educ & Clin, Minneapolis, MN 55417 USA
[2] Vet Affairs Med Ctr, Ctr Chron Dis Outcomes Res, Minneapolis, MN 55417 USA
[3] Univ Calif San Francisco, Dept Epidemiol & Biostat, San Francisco, CA 94143 USA
[4] Univ Calif San Diego, La Jolla, CA 92093 USA
[5] Univ Pittsburgh, Div Epidemiol, Pittsburgh, PA 15260 USA
[6] Oregon Hlth & Sci Univ, Dept Med, Portland, OR 97239 USA