[1] Univ Calif San Francisco, Div Gen Internal Med, San Francisco, CA 94115 USA
[2] Univ Calif San Francisco, Dept Epidemiol & Biostat, San Francisco, CA 94115 USA
[3] Vet Affairs Med Ctr San Francisco, Dept Med, San Francisco, CA USA
[4] Kaiser Permanente No Calif, Div Res, Oakland, CA USA
[5] Univ Pittsburgh, Dept Epidemiol, Pittsburgh, PA 15261 USA