1. Department of Preventive Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
2. Department of Preventive Medicine, College of Medicine, Chosun University, Kwangju, Korea.
3. Department of Preventive Medicine, Medical College of Ewha Womens University, Seoul, Korea.
4. Department of Preventive Medicine, Graduate School of Health Science and Management, Yonsei University, Seoul, Korea.