1. Department of Family Medicine, Chung-Ang University Medical Center, Seoul, Korea.
2. Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Otorhinolaryngology-Head and Neck Surgery, Chung-Ang University College of Medicine, Seoul, Korea.
4. Department of Nursing, Chung-Ang University, Seoul, Korea.
5. Department of Family Medicine, Chung-Ang University College of Medicine, Seoul, Korea.