1. Department of Geriatric Medicine, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, P.R. China
2. International Medical Center, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, P.R. China
3. National Clinical Research Center for Geriatric Disorders, Changsha 410008, Hunan Province, P.R. China