1. Graduate School of Public Health; The Catholic University of Korea; Seoul Korea
2. Department of Dentistry; College of Medicine; The Catholic University of Korea; Seoul Korea
3. Departmentof Biostatistics; College of Medicine; The Catholic University of Korea; Seoul Korea
4. Department of Preventive Medicine; College of Medicine; The Catholic University of Korea; Seoul Korea
5. Catholic Medical Center; The Catholic University of Korea; Seoul Korea
6. Department of Dental Hygiene; Namseoul University; Cheonan Korea
7. Department of Family Medicine; College of Medicine; The Catholic University of Korea; Seoul Korea
8. Department of Epidemiology and Biostatistics; Arnold School of Public Health; University of South Carolina; Columbia SC USA