1. Department of Otorhinolaryngology–Head and Neck Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, South Korea
2. Medical Research Collaborating Center, Seoul National University Bundang Hospital, Seongnam, South Korea
3. Department of Otorhinolaryngology–Head and Neck Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea
4. Department of Otorhinolaryngology–Head and Neck Surgery, The Catholic University of Korea School of Medicine, Seoul, South Korea
5. Department of Otorhinolaryngology–Head and Neck Surgery, Kyung Hee University School of Medicine, Seoul, South Korea
6. Department of Otorhinolaryngology–Head and Neck Surgery, Yonsei University College of Medicine, Seoul, South Korea
7. Division of Chronic Disease Surveillance, Korea Centers for Disease Control and Prevention, Chung Won, South Korea