Impact of body composition on airway inflammation: analyzing FeNO z-scores in non-asthmatic school-aged children...

Background. Obesity is associated with worse asthma outcomes, partly due to inflammasome-mediated neutrophilic Type IVc immunity. However, the impact of adiposity on Type IVb airway inflammation remains poorly understood. This study aimed to evaluate the effect of body fat on Type 2 (T2) airway inflammation, measured using fractional exhaled nitric oxide (FeNO). Methods. This community-based cross-sectional study included 726 children aged 7-12 years (48.9% female) from 71 classrooms in 20 public schools. Anthropometry and bioelectrical impedance analysis assessed body mass index (BMI) category, total body fat (%), fat mass (kg), fat-free mass (kg) and trunk-predicted muscle mass (%). FeNO levels were measured to evaluate airway inflammation and converted into height- and sex-adjusted z-scores (zFeNO) using generalized additive models for location, scale and shape (GAMLSS). Linear regression models were applied to assess associations between BMI classifications and body composition measures with zFeNO. Children with asthma (n=45) were excluded. Results. Mean zFeNO was 0.78 (±2.64). After adjustment for sex, age, parental education, second-hand smoke exposure, caffeine intake, and allergic sensitisation, children classified as overweight according to the International Obesity Task Force had lower zFeNO than normal-weight peers (adjusted β [aβ] -0.63; 95% CI: -1.26 to -0.02). Similar findings were observed among overweight males classified by CDC (aβ -0.96; 95% CI: -1.88 to -0.03). Conclusions.  Height- and sex-adjusted FeNO z-scores were established, and overweight was associated with lower zFeNO in school-aged children. BMI and body composition should be considered when interpreting FeNO as a biomarker of airway inflammation in children.