1. Department of Public Health and Preventive Medicine, Baotou Medical College, The Clinical Epidemiology of Research Center, The First Affiliated Hospital of Baotou Medical College, Baotou, Inner Mongolia, People’s Republic of China
2. Department of Cancer Epidemiology, National Cancer Center, National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, People’s Republic of China
3. School of Public Health, Dalian Medical University, Dalian, People’s Republic of China