1. Department of Family Medicine, Wonkwang University Sanbon Hospital, Gunpo, Korea
2. Department of Economics, Texas A&M University, Texas, USA
3. Department of Epidemiology and Biostatistics, Arnold School of Public Health, University of South Carolina, Columbia, SC, USA
4. Workplace Health Institute, Total Health Care Center, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea
5. Department of Family Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea