1. Department of Epidemiology, College of Preventive Medicine, Third Military Medical University (Army Medical University), Chongqing, China
2. College of Public Health, Southwest Medical University, Luzhou, Sichuan, China
3. West China School of Clinical Medicine, Sichuan University, Chengdu, Sichuan, China
4. College of Public Health, Southwest Medical University, Luzhou, Sichuan 646000, China
5. Department of Epidemiology, College of Preventive Medicine, Third Military Medical University (Army Medical University), Chongqing 400038, China