1. Department of Occupational and Environmental Medicine, Sungkyunkwan University School of Medicine, Seoul, South Korea;
2. Center for Cohort Studies, Total Healthcare Center, Sungkyunkwan University School of Medicine, Seoul, South Korea;
3. Department of Clinical Research Design & Evaluation, Sungkyunkwan University, Seoul, South Korea;
4. Department of Physical Education, Seoul National University, Seoul, South Korea;
5. Department of Internal Medicine, Sungkyunkwan University School of Medicine, Seoul, South Korea