[1] NIA, Clin Res Branch, Longitudinal Studies Sect, Baltimore, MD 21225 USA
[2] Natl Inst Hlth & Welf, Div Welf & Hlth Policies, Helsinki, Finland
[3] Univ Maryland, Sch Med, Dept Epidemiol & Prevent Med, Baltimore, MD 21201 USA
[4] Azienda Sanit Firenze, Geriatr Unit, Florence, Italy
[5] Johns Hopkins Univ, Bloomberg Sch Publ Hlth, Baltimore, MD USA
[6] Univ Jyvaskyla, Dept Hlth Sci, Finnish Ctr Interdisciplinary Gerontol, Jyvaskyla, Finland
[7] NIA, Lab Epidemiol Demog & Biometry, Bethesda, MD USA