1. Department of Geriatrics, The Third Hospital of Changsha City, Changsha, Hunan Province, P.R. China
2. Department of Geriatrics, Xiangya Hospital, Central South University, Changsha, Hunan Province, P.R. China
3. Department of Cardiovascular Medicine, Xiangya Hospital, Central South University, Changsha, Hunan Province, P.R. China