[The impact of obesity on lung function and asthma control in adolescent asthma patients]

Objective: To explore the relationship between obesity and lung function, fractional exhaled nitric oxide (FeNO) levels, and asthma control in children and adolescents with asthma. Methods: A retrospective cohort study. A retrospective analysis was conducted on 1 108 asthmatic children aged 10-18 years who were treated at the Department of Respiratory Children's Hospital of Chongqing Medical University between January 2019 and May 2023. Demographic characteristics, asthma control levels, and lung function data were collected. Based on the World Health Organization body mass index Z-score (BAZ), patients were divided into an obesity group (BAZ >2) and a non-obesity group (BAZ ≤2). The correlations of BAZ with lung function, FeNO levels, and asthma control were analyzed. Group comparisons were performed using independent samples t-test, Mann-Whitney U test, χ² test, or Fisher's exact test, as appropriate. A mixed-effects model was employed to assess associations between variables. Results: Among the 1 108 asthmatic children, 749 were male and 359 were female, 155 were in the obesity group and 953 in the non-obesity group. The obesity group had a higher neutrophil count than the non-obesity group (P<0.05). The mixed-effects model indicated that the obesity group had a higher risk of poor asthma control (OR=1.40 (95%CI 1.05-1.86), P=0.022). BAZ was positively correlated with forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV₁) (β=0.05 (95%CI 0.04-0.06), β=0.03 (95%CI 0.02-0.04), both P<0.001), but negatively correlated with the FEV₁/FVC ratio and forced expiratory flow at 75% of FVC (β=-0.73 (95%CI -0.95--0.51) and -0.03 (95%CI -0.04--0.01), respectively; both P<0.001). No significant correlation was found between BAZ and FeNO levels (P>0.05). Stratified analysis by sex revealed that obesity had a greater impact on FVC, FEV₁, and peak expiratory flow in females than in males (β_female=0.11 (95%CI 0.09-0.13), 0.07 (95%CI 0.05-0.09), 0.20 (95%CI 0.15-0.24), β_male=0.04 (95%CI 0.03-0.06), 0.03 (95%CI 0.02-0.04), 0.11 (95%CI 0.07-0.14), Z=4.92, 3.52, 2.95, all P<0.05). Conclusions: Adolescents with obesity and asthma exhibit a compensatory increase in lung volume accompanied by aggravated airflow limitation. Female patients may be more susceptible to the negative effects of obesity on lung function. No significant correlation was found between BAZ and FeNO levels. Obese children with asthma face a higher risk of poor asthma control.