1. Laboratory of Epidemiology, Demography and Biometry, National Institute on Aging, Bethesda, Maryland
2. Department of Clinical and Experimental Medicine, University of Ferrara, Ferrara, Italy
3. Departments of Medicine and Epidemiology, the Johns Hopkins Medical Institutions, Baltimore, Maryland
4. MedStar Research Institute, Washington, DC
5. Geriatric Department, “I Fraticini,” Italian National Institute for Research and Care on Aging (INRCA), Florence, Italy