1 Department of Epidemiology, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, No. 16766 Jingshi Road, Ji'nan, 250014, Shandong Province, China.
2 Department of Epidemiology, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, No. 16766 Jingshi Road, Ji'nan, 250014, Shandong Province, China; Shandong Provincial Qianfoshan Hospital, Cheeloo College of Medicine, Shandong University, China. Electronic address: Ruipingma@126.com.