1. Department of Gastroenterology, Ajou University School of Medicine, Suwon, Korea.
2. Department of Pediatrics, Gachon University of Medicine and Science, Incheon, Korea.
3. Incheon Metropolitan Government Research Institute of Public Health and Environment, Incheon, Korea.
4. Department of Preventive and Social Medicine, College of Medicine, Inha University, Incheon, Korea.