1. Department of Epidemiology and Health Statistics, Xiangya School of Public Health, Central South University, Changsha, Hunan Province 410078, China
2. Division of Recruitment and Employment, University of South China, Hengyang, Hunan Province 421001, China
3. Department of Cardiology, The First Affiliated Hospital of University of South China, Hengyang, Hunan Province 421001, China