1 Department of Epidemiology and Health Statistics, School of Public Health, Anhui Medical University, Hefei 230032, China; The Fifth Sanatorium for Retired Cadres, Anhui Provincial Military Region.
2 Department of Epidemiology and Health Statistics, School of Public Health, Anhui Medical University, Hefei 230032, China.
3 Department of Epidemiology and Health Statistics, School of Public Health, Anhui Medical University, Hefei 230032, China. Email: yhsun@sina.com.