1. Department of Gastroenterology and Endoscopy, The First Hospital of China Medical University, Shenyang 110001, Liaoning, P.R. China
2. Department of Geriatrics, The First Hospital of China Medical University, Shenyang 110001, Liaoning, P.R. China
3. Department of Endodontics, School of Stomatology, China Medical University, Shenyang 110001, Liaoning, P.R. China
4. Department of International Physical Examination Center, The First Hospital of China Medical University, Shenyang 110001, Liaoning, P.R. China