1. Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, You’anmenwai, Xitoutiao No.10, Beijing, P. R. China
2. Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, P. R. China
3. Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, P. R. China
4. Department of Orthopaedics and Neurosurgery, Keck Medical Center of USC, Los Angeles, CA, USA
5. School of Computer Science and Technology, University of the Chinese Academy of Sciences, Beijing, P. R. China
6. Department of Psychology, Emory University, Atlanta, GA, USA