1. Department of Family Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
2. Department of Family Medicine, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
3. Department of Family Medicine, Kangwon National University Hospital, Kangwon National University College of Medicine, Chuncheon, Korea.
4. Health Promotion Center, Seoul National University Bundang Hospital, Seongnam, Korea.