1. Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland.
2. Department of Medical and Surgical Sciences, University of Bologna, Italy.
3. Department of Epidemiology and Public Health, Division of Gerontology, University of Maryland School of Medicine, Baltimore.
4. Department of Geriatric Medicine, ASF – Firenze, Florence, Italy.
5. Division of Geriatric Medicine and Gerontology, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland.