Study population
In this study, a total of 1,797 children aged 9–12 years were recruited from Seoul and Jeongeup cities in Korea. Of the total children recruited, 351 who did not answer questions related to AR in the questionnaire were excluded from the analysis. Current AR patients were defined as children who were diagnosed with AR by the physician and had AR symptoms during the last 12 months based on the questionnaire. This study was conducted with approval from the institutional review boards of Hallym University and University of Ulsan College of Medicine and the principals of the children’s school (IRB number: 2008-0208).