1. Department of Epidemiology, School of Public Health, Inner Mongolia Medical University, Inner Mongolia Autonomous Region, Hohhot 010110, P.R. China
2. Laboratory for Molecular Epidemiology in Chronic Diseases, School of Public Health, Inner Mongolia Medical University, Inner Mongolia Autonomous Region, Hohhot 010110, P.R. China
3. College of Continuing Education (IMAU Branch of Educational and Training Center for Central Agricultural Cadre), Inner Mongolia Agricultural University, Inner Mongolia Autonomous Region, Hohhot 010110, P.R. China