1. Department of Gastroenterology, Beijing Friendship Hospital, Capital Medical University , Beijing 100050 , China
2. National Clinical Research Center for Digestive Diseases , Beijing 100050 , China
3. Beijing Digestive Disease Center , Beijing 100050 , China
4. Department of Presbyatrics, Beijing Friendship Hospital, Capital Medical University , Beijing 100050 , China
5. Department of Clinical Epidemiology and Evidence-based Medicine, Beijing Friendship Hospital, Capital Medical University , Beijing 100050 , China