1. Department of Family Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
2. Department of Family Medicine, Samsung Medical Center, and Center for Clinical Research, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, Korea.
3. Research and Development Center, Health Insurance Review and Assessment Service, Seoul, Korea and Interdepartmental Program in Social Public Health, Graduate School, Hallym University, Chuncheon, Korea.