1. Geriatric Unit, Department of Medical Sciences & Gerontology and Geriatrics Laboratory, Research Department, IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy.
2. National Institute on Aging, Longitudinal Studies Section, Harbor Hospital Center, Baltimore, Maryland.
3. CSS-Mendel Institute, Department of Research, Rome, Italy.
4. Biostatistics & Gastroenterology Unit, IRCCS Saverio De Bellis, Castellana Grotte, Italy.