1. Department of Epidemiology and Health Statistics, School of Public Health and Management, Ningxia Medical University, Yinchuan, Ningxia, China.
2. Department of Nutrition and Food Hygiene, School of Public Health and Management, Ningxia Medical University, Yinchuan, Ningxia, China.
3. Key Laboratory of Environmental Factors and Chronic Disease Control, Yinchuan, Ningxia, China.