Ethical approval
This study was conducted with approval from the institutional review boards of Hallym University and the University of Ulsan College of Medicine and the principals of the children’s school (IRB number: 2008-0208). Written informed consent was obtained from the parents of all the children prior to study initiation. The obtainment of consent was confirmed by the IRB.
Authorship: Choi EJ, Lee SY, and Hong SJ designed and wrote the manuscript and performed the analyses. Kun Baek Song, Eun Young Baek, Min Ji Park, Jisun Yoon, Sungsu Jung, Si Hyeon Lee, Mi-Jin Kang, Hea Young Oh, and Kang Seo Park participated in the collection, analysis, and interpretation of the data. Hong SJ and Lee SY supervised the execution of the study.