1. Department of Geriatrics, Xijing Hospital, Fourth Military Medical University, Xi’an, P.R. China
2. Department of Geriatrics, Xi’an Central Hospital, Xi’an, P.R. China
3. Department of Cardiology, Traditional Chinese Medicine Hospital of Baoji City, Baoji, P.R. China
4. Department of Cardiology, Shengli Oilfield Central Hospital, Dongying, P.R. China
5. Department of Physiology, Fourth Military Medical University, Xi’an, P.R. China