1. Department of Health Services Management, Kyung Hee University, Seoul, Korea.
2. Department of Preventive Medicine, School of Medicine, Graduate School of Ewha Womans University, Seoul, Korea.
3. Department of Medical Sciences, Graduate School of Ewha Womans University, Seoul, Korea.
4. Korean Academy of Medical Sciences, and College of Medicine, Chung-Ang University, Seoul, Korea.
5. Korean Academy of Medical Sciences, and College of Medicine, Kyung Hee University, Seoul, Korea.