Association between body mass index and asthma symptoms among Korean children: a nation-wide study.

The purpose of this study was to investigate the association between body mass index (BMI) and the prevalence of wheeze using nation-wide cross-sectional study in Korean children. Total 50,200 children from 427 elementary schools were randomly selected according to residential areas (metropolitan, provincial, rural, and industrial areas) by the cluster sampling method. The International Study of Asthma and Allergies in Childhood (ISAAC) questionnaires were used to measure the prevalence of wheeze. Among 31,026 respondents, 25,322 were analyzed. BMI was classified into quartiles based on BMI-for-age percentile. In all residential areas, pets at home and visible mold or moisture were associated with an increased prevalence of wheeze in both genders. However, other living environment factors were not consistently associated among residential areas and gender. Among girls, lowest BMI was negatively associated with prevalence of wheeze and highest BMI was positively associated in all residential areas. In multilevel logistic regression analysis, environmental tobacco smoking exposure, pets at home, visible mold or moisture, and being in the lowest and highest BMI quartile were significantly associated with the prevalence of wheeze in both genders. BMI has become an important risk factor for asthma symptoms among Korean children.