1. Department of Family Medicine (S.Y.J.), Yeouido St Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul 150-713, Korea
2. Department of Preventive Medicine (H.S.J.), Seoul St Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea
3. Department of Family Medicine (D.H.K.), Korea University Ansan Hospital, Korea University College of Medicine, Seoul 136-705, Korea