作者单位:UCLA, David Geffen Sch Med, Dept Med, UCLA Robert Wood Johnson Clin Scholars Program, Los Angeles[1]UCLA, David Geffen Sch Med, Dept Med, Div Geriatr, Los Angeles, CA 90095 USA[2]RAND Corp, Hlth Unit, Santa Monica, CA USA[3]UCLA, Dept Hlth Policy & Management, Fielding Sch Publ Hlth, Los Angeles, CA USA[4]Univ Calif Davis, Dept Med, Davis, CA 95616 USA[5]