Association of vitamin D with disease severity in infants with bronchiolitis

Vitamin D's role in immune system regulation and its contribution to host defenses against respiratory infections may have implications for bronchiolitis pathophysiology. This cross-sectional study aimed to determine the association between the clinical severity of bronchiolitis and serum vitamin D levels in infants. Infants aged 1 month to 12 months, diagnosed with bronchiolitis, and healthy controls attending routine immunization were enrolled. Baseline characteristics were recorded, including clinical details, bronchiolitis severity, and course during hospital stay. Bronchiolitis severity score (BSS) was used to score the severity. A 1-2 ml serum sample was obtained for vitamin D levels estimation. The median age of cases (n = 64; 65.6% male) was 5 [3, 8] months, and that of the control group (n = 30) was 3 [2, 9] months. No statistically significant differences were observed between the two groups in age, gender, weight, mode of delivery, family history of atopy/asthma, feeding pattern, smoke exposure, and daily vitamin D supplementation. The median vitamin D levels were not significantly different between the groups (p = 0.68). Among infants with bronchiolitis, 62.5% had vitamin D insufficiency (≤ 20 ng/ml). A significantly higher median BSS indicates that infants with vitamin D insufficiency exhibited more severe disease (p = 0.019). Although a negative correlation between BSS and vitamin D levels was noted, it did not reach statistical significance [r_s = (-)0.17; p = 0.16].

Infants with Vitamin D insufficiency experienced more severe bronchiolitis with elevated BSS scores. It highlights the potential role of vitamin D deficiency in severe bronchiolitis.

• Vitamin D level is low in infants with bronchiolitis.

• Infant with low vitamin D level experienced more severe bronchiolitis.