The aim of this study was to evaluate the association between obesity and asthma in a population-based sample of Canadian children. Baseline data from the National Longitudinal Survey of Children and Youth were used in this cross-sectional study. We included 11,199 children age 4 to 11 years whose biological mother reported data on asthma, height, and weight. Body mass index was categorized, and obesity was defined as body mass index at or greater than the 85th percentile. Children with asthma had parents who reported the diagnosis, and they took prescribed inhalants, had wheezing or an attack in the previous year, or had their activities limited by asthma. Multiple logistic regression was used.

The prevalence of asthma was 9.9%. Maternal history of asthma was a risk factor for asthma among all children. Single child status and maternal depression were risk factors for girls. The odds ratio for asthma, comparing highest and lowest body mass index categories, was 1.02 (99% confidence interval, 0.70–1.46) for boys and 1.06 (99% confidence interval, 0.67–1.69) for girls.