1. School of Public Health, North China University of Science and Technology, Tangshan, China
2. Institute for Nutrition and Food Safety, Hebei Provincial Center for Disease Control and Prevention, Shijiazhuang, China
3. National Institute for Nutrition and Health, Chinese Center for Disease Control and Prevention, Beijing, China
4. Department of Epidemiology, Wuqiang Center for Disease Control and Prevention, Hengshui, China