Risk factor for impaired lung function in asthmatic children: predictive value of 25-OH-D, BMI and inflammatory...

This cross-sectional study investigated the associations between modifiable metabolic risk factors (vitamin D status and obesity) and pulmonary function decline in children with asthma, independent of disease duration and airway inflammation.

Medical records of 430 asthmatic children (aged ≤14 years) were retrospectively analyzed. Using FEV1%pred <80% as the cutoff, 171 children with pulmonary function impairment were compared with 259 children with normal pulmonary function. Clinical characteristics, pulmonary function parameters, and laboratory indices (25-(OH)-D, BMI, CRP, IL-6, TNF-α) were collected. Multivariate logistic regression and receiver operating characteristic (ROC) analyses were performed.

Among the 430 enrolled children, 171 (39.75%) presented with pulmonary function impairment, predominantly of mild-to-moderate severity. Compared with children with normal pulmonary function, those with impaired pulmonary function had longer disease duration, lower ACT scores, decreased 25-(OH)-D levels, and elevated BMI, CRP, IL-6, and TNF-α levels (all P<0.05). 25-(OH)-D levels were positively correlated with FEV1%pred and FEV1/FVC, and negatively correlated with BMI, CRP, IL-6, and TNF-α (all P<0.001). Multivariate logistic regression analysis identified prolonged disease duration (OR=1.789, 95% CI: 1.333-2.401), elevated BMI (OR=1.205, 95% CI: 1.035-1.403), increased IL-6 (OR=1.193, 95% CI: 1.086-1.312), elevated CRP (OR=1.362, 95% CI: 1.118-1.658), and secondhand smoke exposure (OR=3.336, 95% CI: 1.567-7.102) as independent risk factors for pulmonary function impairment (all P<0.05). Conversely, higher ACT scores (OR=0.763, 95% CI: 0.675-0.861) and 25-(OH)-D levels (OR=0.818, 95% CI: 0.730-0.916) were associated with a lower likelihood of pulmonary function impairment (all P<0.01). Ten-fold cross-validated ROC analysis demonstrated that the mean AUC values of 25-(OH)-D, BMI, IL-6, CRP, and TNF-α were 0.883, 0.806, 0.862, 0.845, and 0.827, respectively.

Vitamin D status and secondhand smoke exposure were significantly associated with pulmonary function impairment in children with asthma. Our findings suggest a metabolic component in childhood asthma, although causal inference is limited by the cross-sectional design. Prospective studies are warranted to validate these associations and further clarify underlying mechanisms.