1. Department of Pulmonary and Critical Care Medicine, Changzheng Hospital, Second Military Medical University, Shanghai 200003, P.R. China
2. Department of Gastroenterology, Changzheng Hospital, Second Military Medical University, Shanghai 200003, P.R. China
3. Department of Endocrinology, Changzheng Hospital, Second Military Medical University, Shanghai 200003, P.R. China
4. Department of Health Statistics, Second Military Medical University, Shanghai 200433, P.R. China