Department of Epidemiology School of Public health Hainan Medical University Haikou Hainan 571199 China;
Department of Epidemiology School of Public health Hainan Medical University Haikou Hainan 571199 China;
Department of Epidemiology School of Public health Hainan Medical University Haikou Hainan 571199 China;
Department of Epidemiology School of Public health Hainan Medical University Haikou Hainan 571199 China;