Pediatric Pulmonology 49:1049–1057 (2014) Differing Associations of BMI and Body Fat With Asthma and Lung Function in Children

Summary. Background: Current evidence suggests that in children there is a significant, albeit weak, association between asthma and obesity. Studies generally use body mass index (BMI) in evaluating body adiposity, but there are limitations to its use. Method: Children from a population-based study attending follow-up (age 11 years) were weighed, measured and had percent body (PBF) and truncal (PTF) fat assessed using bioelectrical impedance. They were skin prick tested and completed spirometry. Parents completed a validated respiratory questionnaire. Children were defined as normal or overweight according to BMI and PBF cut-offs. We tested the association between these adiposity markers with wheeze, asthma, atopy, and lung-function. Results: Six hundred forty-six children (339 male) completed follow-up. BMI z-score, PBF, and PTF were all positively associated with current wheeze (odds ratio [95 % CI]: 1.27 [1.03, 1.57], P0.03; 1.05 [1.00, 1.09],P0.03; 1.04 [1.00, 1.08],P0.04, respectively). Similar trendswere seen with asthma. However, when examining girls and boys separately, significant positive associations were found with PBF and PTF and asthma but only in girls (gender interaction P0.06 and 0.04, respectively). Associations between being overweight and wheezing and asthmawere strongerwhen overweight was defined byPBF (P0.007, 0.03) thanBMI (P>0.05). Higher BMI was significantly associated with an increase in FEV1 and FVC, but only in girls. Conversely, increasing body fat (PBF and PTF) was associated with reduced FEV1 and FVC, but only in boys. No associations between adiposity and atopy were found. Conclusion: All adiposity measures were associated with wheeze, asthma, and lung function. However, BMI and PBF did not have the same effects and girls and boys appear to be affected differently. Pediatr Pulmonol