1 Evidence-based Medical Center, Xuanwu Hospital, Capital Medical University, Beijing 100053, China; National Clinical Medical Research Center for Geriatric Disorders, Xuanwu Hospital, Capital Medical University, Beijing 100053, China.
2 National Clinical Medical Research Center for Geriatric Disorders, Xuanwu Hospital, Capital Medical University, Beijing 100053, China; Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing 100053, China. Electronic address: ggzhao@vip.sina.com.