Is obesity a risk factor for childhood asthma?

Background: In adolescents and adults, an association between obesity and asthma was found in females. Does this sex-specific association already exist in young children? Methods: Questionnaire data on 9357 5- and 6-year-old German children were collected in 1997 in two rural regions in Bavaria. The diagnosis of asthma, hay fever, and eczema was ascertained with the ISAAC core and other validated questions. Overweight was defined by a BMI of > 90th and less than or equal to 97th percentile and obesity by a BMI of >97th percentile. Results: The lifetime prevalence of doctor's diagnosed asthma in girls was 3.5% (95% CI 2.9-4.1%) for normal weight, 5.8% (95% CI 3.2-8.4%) for overweight, and 10.3% (95% CI 5.3-15.2%) for obesity, whereas no relation to weight was found in boys. Hay fever and eczema were unrelated to weight in girls and boys. The adjusted odds ratio for asthma in girls was 2.12 (95% CI 1.22-3.68) for overweight and 2.33 (95% CI 1.13-4.82) for obesity. Conclusions: A sex-specific association with doctor's diagnosed asthma was also observed in girls at school entry. Since this association was confined to doctor's diagnosed asthma in the absence of other atopic conditions, and no association with other atopic manifestations was found, we hypothesize that this association is related to factors other than atopic sensitization.