1. Department of Epidemiology and Health Statistics; Xiangya School of Public Health; Central South University; Changsha China
2. Hunan University of Medicine; Huaihua China
3. Department of Dermatology; Xiangya Hospital; Central South University; Changsha China
4. Ningxiang General Hospital; Ningxiang China
5. OMNI Research Group; Department of Obstetrics and Gynecology; Faculty of Medicine; University of Ottawa; Ottawa ON Canada
6. Ottawa Hospital Research Institute; Clinical Epidemiology Program; University of Ottawa; Ottawa ON Canada
7. School of Epidemiology and Public Health; Faculty of Medicine; University of Ottawa; Ottawa ON Canada