1. Division of Emergency Department, Xuan Wu hospital of Capital Medical University, Beijing, China
2. Department of Emergency Medicine, University of California, Davis, Davis, CA, United States
3. Department of Neurobiology, Neurology and Geriatrics, Xuanwu Hospital of Capital Medical University, Beijing Institute of Geriatrics, Beijing, China and National Clinical Research Center for Geriatric Disorders, Beijing, China;, Email: pbchan@hotmail.com