The association of vitamin D deficiency with the severity of adenoid hypertrophy and allergic rhinitis in children: a retrospective observational study.

Background: Allergic rhinitis (AR) and adenoid hypertrophy (AH) are common pediatric comorbidities. Vitamin D is a known immunomodulator, but its relationship with the concurrent severity of AR and AH remains unclear. We aimed to investigate the association between serum 25-hydroxyvitamin D [25(OH)D] levels and disease severity in children with both conditions. Methods: This retrospective study included 268 children (3-12 years) with co-existing AR and AH. We collected data on serum 25(OH)D, adenoidal-nasopharyngeal (A/N) ratio, total and specific IgE, and symptom scores. Patients were stratified by 25(OH)D levels: severe deficiency (<10), deficiency (10-<20), insufficiency (20-<30), and sufficiency (≥30 ng/mL). Multiple linear/logistic regression and restricted cubic spline (RCS) analyses were performed. Results: The mean 25(OH)D level was 17.7 ± 6.8 ng/mL, with a high prevalence of deficiency (70.5% < 20 ng/mL). Serum 25(OH)D levels were significantly and inversely correlated with A/N ratio ( Conclusion: Vitamin D deficiency is highly prevalent and independently associated with increased severity of both adenoid hypertrophy and allergic inflammation in children with AR and AH. This association is most pronounced at lower vitamin D concentrations, suggesting that vitamin D status may play a role in the pathophysiology of these conditions and that correcting deficiency could be a valuable adjuvant therapeutic strategy.