1. Department of Epidemiology, School of Public Health, Sun Yat-sen University, No. 74, 2nd Yat-sen Road, Yuexiu District, Guangzhou 510080, China
2. Center for Health Care, Longhua District, Shenzhen 518109, China
3. Department of Epidemiology and Biostatistics, College of Public Health, Zhengzhou University, Zhengzhou 450001, China