Bin Yu1, Xinguang Chen2, Shiyue Li3. 1. Department of Epidemiology and Health Statistics, School of Public Health of Wuhan University; Globe Health Center, Wuhan University, Wuhan 430071, China. 2. Globe Health Center, Wuhan University, Wuhan 430071, China; School of Medicine and Pediatrics Prevention Research Center, Wayne State University. 3. Department of Epidemiology and Health Statistics, School of Public Health of Wuhan University; Globe Health Center, Wuhan University, Wuhan 430071, China. Email: lsywhd@sina.com.