1 Department of Preventive Medicine, College of Medicine, Ewha Womans University, Seoul, South Korea.
2 Division of Cardiology, Department of Internal Medicine, Ewha Womans University Mokdong Hospital, College of Medicine, Ewha Womans University, Seoul, South Korea.
3 Division of Nephrology, Department of Internal Medicine, Ewha Womans University Seoul Hospital, College of Medicine, Ewha Womans University, Seoul, South Korea.