Extreme BMI Predicts Higher Asthma Prevalence and Is Associated With Lung Function Impairment in School-Aged Children

Background: The prevalence of obesity and asthma has increased in recent decades. We investigated the relationship between body mass index (BMI) and lung function, and also tried to determine if asthma prevalence differs between obese and non-obese children. Methods: An International Study of Asthma and Allergies in Childhood (ISAAC) video questionnaire survey that included 170,457 students in junior high school was conducted during a 1-year period. Using random selection, 15,761 students were selected for lung function testing; 14,654 (93.0%) completed the lung function tests. Multiple logistic regression analysis was used to analyze the risk factor of asthma, such as atopic diathesis, BMI, exercise habits, smoking and secondary smoking. The detailed comparison in lung functions was plotted by asthmatic versus non-asthmatic, and between both sexes. Results: The risk factor of ISAAC-identified asthma were male sex, atopy, elevated BMI, higher education levels of the parents (higher than senior high school), family smoking >= 1 pack/day, self-reported smoking. The prevalence of asthma increased as BMI elevated in both sex. The FEV1/FVC declined as BMI elevated in both sex. The thin and underweight male students had declined FEF 25-75% and PEF Conclusions: Extreme BMI is associated with different lung function impairment. This study showed that high BMI in both sexes was associated with low FEV1/FVC and low BMI in males are associated with poor PEF and FEF 25-75% and contributed to the symptoms of asthma. Pediatr Pulmonol. 2009;44: 472-479. (C) 2009 Wiley-Liss, Inc.