A persistently high body mass index increases the risk of atopic asthma at school age

AIM: Being overweight has been associated with the risk of developing childhood asthma, but studies have produced conflicting results, for example with regard to possible links to allergic diseases. This study aimed to explore the relationship between body mass index (BMI) and school-age asthma. METHODS: Data were obtained from a prospective, longitudinal study of 5044 children born in western Sweden. The parents answered questionnaires at six months and one, four-and-a-half and eight years of age. The response rate to the final questionnaire at the age of eight was just over 80%. BMI was adjusted for age and gender, and a high BMI was defined as the 85th percentile and above. RESULTS: A multivariate analysis showed an independently increased risk of doctor-diagnosed asthma among children with a persistently high BMI, both in infancy and at school age, with an adjusted odds ratio (aOR) of 2.9 and a 95% confidence interval (CI) of 1.3–6.4. In addition, persistently high BMI was associated with an increased risk of atopic asthma (aOR 4.7, 95% CI 2.0–11.0). CONCLUSION: A persistently high BMI during childhood increased the risk of doctor-diagnosed asthma at school age. The increased risk of atopic asthma suggests an effect mediated via the immune system.