1. Department of Medicine and
2. Department of Preventive Medicine, Northwestern University Medical School, Chicago, Illinois;
3. Epidemiology , Demography, and Biometry Program, National Institute on Aging, Bethesda, Maryland;
4. Geriatric Department , “I Fraticini,” National Research Institute (INRCA), Florence, Italy; and
5. Johns Hopkins University Medical School , Baltimore, Maryland.