1. Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.
2. Department of Preventive Medicine, Eulji University College of Medicine, Daejeon, Korea.
3. Department of Biostatistics, Seoul National University School of Public Health, Seoul, Korea.
4. Department of Preventive Medicine, Dongguk University College of Medicine, Gyeongju, Korea.
5. Department of Pediatrics, Yonsei University College of Medicine, Seoul, Korea.
6. Department of Pediatrics, Handong University Sunlin Hospital, Pohang, Korea.
7. Department of Social and Preventive Medicine, Sungkyunkwan University School of Medicine, Suwon, Korea.