1. The Second Medical Center and National Clinical Research Center for Geriatric Diseases, Chinese PLA General Hospital, Medical School of Chinese PLA, Beijing, China
2. Department of Obstetrics and Gynecology, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, Shaanxi, China
3. Department of Emergency, The Second Medical Center and National Clinical Research Center for Geriatric Diseases, Chinese PLA General Hospital, Beijing, China
4. The Third Medical Center, Chinese PLA General Hospital, Medical School of Chinese PLA, Beijing, China