1. Department of Family Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
2. Health Promotion Center, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, South Korea.
3. Department of Epidemiology, School of Public Health and Institute of Health Environment, Seoul National University, Seoul, South Korea.
4. Department of Family Medicine, Busan Paik Hospital, Inje University, College of Medicine, Busan, South Korea.
5. Department of Family Medicine, Konkuk University Medical Center, Seoul, South Korea.