1. Geriatric Unit, Campus Bio-Medico University, Rome, Italy
2. Laboratory of Clinical Epidemiology, Department of Medicine and Sciences of Aging, University G. D’Annunzio, Chieti, Italy
3. Geriatric Unit, Azienda Sanitaria di Firenze Toscana, Italy
4. National Institute on Aging, National Institutes of Health, Baltimore, Maryland