Serum vitamin D levels in relation to asthma severity, lung function, and type 2 inflammatory biomarkers

Introduction: Vitamin D has important immunomodulatory effects and may play a role in asthma pathophysiology; however, its impact on clinical outcomes remains unclear. The objective of this study was to evaluate the association between serum vitamin D levels and asthma severity, lung function, disease control, and type 2 inflammatory markers. Methods: This prospective cross-sectional study included 60 asthma patients divided into severe (n=30) and mild-to-moderate (n=30) groups. Serum vitamin D levels, FEV₁, ACT score, blood eosinophils, and total IgE were analyzed. Results: Patients with severe asthma had significantly lower vitamin D levels (p=0.008), lower FEV₁ and ACT scores, and higher eosinophil counts. Vitamin D deficiency was significantly more frequent in this group (83.3% vs 56.7%; p=0.047; OR=3.82). A positive correlation was observed between vitamin D levels and FEV₁ (ρ=0.306; p=0.018), as well as ACT score (ρ=0.368; p=0.004), while correlations with eosinophils and IgE were not statistically significant. Conclusion: Lower serum vitamin D levels are associated with greater asthma severity, impaired lung function, and poorer disease control. Vitamin D may act as a disease modifier, although further longitudinal and interventional studies are needed to clarify causality.