1. Department of Medical Statistics, School of Public Health, Sun Yat-sen University, Guangzhou, China
2. Zhongshan Shiqi Suhuazan Hospital, Zhongshan, China
3. Zhongshan Center for Disease Control and Prevention, Zhongshan, China
4. The First Affiliated Hospital, Sun Yat-sen Universtity, Guangzhou, China
5. Community Health Service Center of Shawan Town, Panyu District, Guangzhou, China