1. Department of Family Medicine, Chung-Ang University Hospital, Chung-Ang University College of Medicine, Seoul, Korea.
2. Department of Family Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
3. Department of Family Medicine, Eulji General Hospital, Eulji University School of Medicine, Seoul, Korea.
4. Department of Family Medicine, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
5. Department of Family Medicine, Veterans Health Service Medical Center, Seoul, Korea.
6. Department of Family Medicine, Pyeongtaek International Hospital, Pyeongtaek, Korea.