[1] Univ Calif Berkeley, Sch Publ Hlth, Div Epidemiol, 2121 Berkeley Way,West 5302, Berkeley, CA 94720 USA
[2] Emory Univ, Dept Epidemiol, Rollins Sch Publ Hlth, Atlanta, GA 30322 USA
[3] Univ Michigan, Sch Publ Hlth, Dept Epidemiol, Ann Arbor, MI 48109 USA
[4] Univ Calif San Francisco, Dept Biochem & Biophys, San Francisco, CA USA
[5] Univ Calif Los Angeles, David Geffen Sch Med, Dept Geriatr, Los Angeles, CA 90095 USA