1. College of Public Health, Shandong Second Medical University, Weifang, Shandong, China
2. Dezhou Hospital of Traditional Chinese Medicine, Dezhou, Shandong, China
3. Department of Histology and Embryology, Shandong Second Medical University, Weifang, Shandong, China
4. Department of Epidemiology, Shandong Second Medical University, Weifang, Shandong, China.