D2.136 - Association Between Serum 25-Hydroxyvitamin D Levels and Asthma Severity in Preschool Children

Asthma is a common chronic disease in childhood. Recent studies suggest that vitamin D may play a role in modulating immune responses and airway inflammation; however, its relationship with asthma severity remains unclear. This study aimed to evaluate the association between serum 25-hydroxyvitamin D (s25-OHD₃) levels and asthma severity in preschool-aged children and to assess the impact of vitamin D supplementation in those with deficiency.

This retrospective study included 245 children aged 2–6 years diagnosed with asthma and followed at Ankara Bilkent City Hospital between 2019 and 2024. Data obtained from medical records included demographic characteristics, atopy status, symptom control, treatment steps, and s25-OHD₃ levels. Post-supplementation outcomes were analyzed in a subgroup of patients who received vitamin D replacement.

The mean s25-OHD₃ level was 20.56 ± 9.28 ng/mL. Lower vitamin D levels were significantly associated with higher asthma exacerbation frequency, increased treatment step requirements, and poorer symptom control (p < 0.05). Following supplementation, both vitamin D levels and symptom control improved significantly in deficient patients (p < 0.001).

These findings indicate that lower s25-OHD₃ levels are associated with greater asthma severity in preschool-aged children, and vitamin D supplementation may contribute to improved disease control in those with deficiency. This study provides novel data in an underrepresented age group and supports a potential role for vitamin D in pediatric asthma management.