1. Graduate College, Tianjin Medical University, Tianjin, China
2. Department of Cardiac Surgery, Tianjin Chest Hospital, Tianjin, China
3. Neurology Department, Beijing Hospital, National Center of Gerontology, Dong Dan, Beijing, P. R. China
4. Department of geriatric medicine, Qinghai University, Xining, Qinghai, China
5. Internal medicine, Jinzhou Medical University, Linghe District, Jinzhou City, Liaoning Province, China