[1] Univ Pittsburgh, Dept Epidemiol, Pittsburgh, PA 15261 USA
[2] Calif Pacific Med Ctr, Res Inst, San Francisco, CA USA
[3] Univ Chicago, Hlth Care Dept, NORC, Bethesda, MD USA
[4] Univ Minnesota, Dept Med, Box 736 UMHC, Minneapolis, MN 55455 USA
[5] VA Hlth Care Syst, Ctr Chron Dis Outcomes Res, Minneapolis, MN USA
[6] Kaiser Permanente Northwest, Ctr Hlth Res, Portland, OR USA
[7] Pk Nicollet Clin, St Louis Pk, MN USA
[8] Univ Minnesota, Div Hlth Policy & Management, Minneapolis, MN USA
[9] Univ Calif San Francisco, San Francisco, CA 94143 USA