Vitamin D Status at the Time of Hospitalization for Bronchiolitis and Its Association with Disease Severity

Area of Science:

• Pediatric Respiratory Medicine
• Nutritional Immunology
• Clinical Biochemistry

Background:

• Bronchiolitis is a common respiratory infection in infants, associated with significant hospitalizations.
• Vitamin D plays a crucial role in immune function, and its deficiency is linked to various health outcomes.
• The relationship between vitamin D status and bronchiolitis severity requires further investigation.

Purpose of the Study:

• To examine the association between 25-hydroxyvitamin D [25(OH)D] levels at admission and bronchiolitis severity in hospitalized infants.
• To determine if different forms of vitamin D (total, bioavailable, free) influence this association.

Main Methods:

• Prospective cohort study involving 1016 infants <12 months old across 17 US centers.
• Vitamin D status assessed by total, bioavailable, and free 25(OH)D levels.
• Bronchiolitis severity measured by intensive care unit admission and hospital length-of-stay (LOS); statistical analyses included logistic and Poisson regression.

Main Results:

• Infants with total 25(OH)D <20 ng/mL showed increased risk for intensive care (aOR 1.72) and longer LOS (aRR 1.39) compared to those with ≥30 ng/mL.
• Lowest tertile of bioavailable 25(OH)D was associated with longer LOS (aRR 1.32), but not significantly with ICU admission.
• Free 25(OH)D levels were not associated with bronchiolitis severity.

Conclusions:

• Low total 25-hydroxyvitamin D [25(OH)D] levels (<20 ng/mL) at admission are linked to increased severity in infants hospitalized with bronchiolitis.
• This association suggests vitamin D status is a relevant factor in the clinical course of infant bronchiolitis.
• Further research may explore the therapeutic potential of vitamin D supplementation in this population.