1. Department of Internal Medicine, Jeju National University Hospital, Jeju National University School of Medicine, Jeju, Korea.
2. Institute of Health and Environment, School of Public Health, Seoul National University, Seoul, Korea.
3. Graduate School of Public Health, Seoul National University, Seoul, Korea.
4. Department of Internal Medicine, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
5. Department of Internal Medicine, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Suwon, Korea.
6. Department of Internal Medicine, Hallym University Sacred Heart Hospital, Anyang, Korea.
7. Department of Internal Medicine, Hallym University Kangdong Sacred Heart Hospital, Seoul, Korea.
8. GF Allergy Clinic, Seoul, Korea.
9. Beautiful Breath Clinic, Seoul, Korea.
10. Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA.
11. Department of Internal Medicine, Gwangmyeong Sungae Hospital, Seoul, Korea.
12. Department of Internal Medicine, Sungae Hospital, Seoul, Korea.
13. A&A Clinic, Seoul, Korea.
14. Sanbon Yonsei Clinic, Gunpo, Korea.
15. Department of Internal Medicine, Chonnam National University Hospital, Gwangju, Korea.
16. Department of Internal Medicine, St. Paul's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
17. Department of Internal Medicine, Yeouido St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
18. Department of Internal Medicine, School of Medicine, Ewha Womans University, Seoul, Korea.
19. Department of Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
20. Department of Internal Medicine, Konkuk University School of Medicine, Seoul, Korea.