[1] Duke Univ, Med Ctr, Dept Med, Durham, NC 27709 USA
[2] Vet Affairs Med Ctr, Ctr Hlth Serv Res Primary Care, Durham, NC 27705 USA
[3] Duke Univ, Med Ctr, Dept Biostat & Bioinformat, Durham, NC 27705 USA
[4] Indiana Univ, Ctr Aging Res, Regenstrief Inst Inc, Indianapolis, IN 46202 USA
[5] Univ Washington, Dept Psychiat, Seattle, WA 98195 USA
[6] Grp Hlth Cooperat Puget Sound, Ctr Hlth Studies, Seattle, WA 98101 USA
[7] Kaiser Permanente So Calif, San Diego, CA 92120 USA