Association Between Vitamin D Deficiency and Severity of Acute Respiratory Infections in Pediatric and Adult Patients

Abstract

Background: Vitamin D deficiency is common and may be associated with increased severity of acute respiratory infections (ARIs). Objective: To determine the association between vitamin D deficiency and severity of ARIs among pediatric and adult patients. Methodology: This analytical cross-sectional study was conducted at Pakistan from January to December 2025. The patient population utilized was 200 (100.00%) patients with ARI who were collected by non-probability consecutive sampling which included 100 (50.00%) pediatric and 100 (50.00%) adult patients. The levels of 25(OH)D in the serum were classified as deficient (<20 ng/mL), insufficient (20–29 ng/mL), or sufficient (≥30 ng/mL). Severity of ARI was determined based on age-appropriate clinical criteria. Chi-square/Fisher's exact and multivariable logistic regression were used to analyze associations and p<0.05 was considered statistically significant. Results: Vitamin D deficiency was present in 106 (53.00%) patients, including 57 (57.00%) pediatric and 49 (49.00%) adult patients. Severe ARI occurred in 36 (33.96%) vitamin D-deficient patients compared with 9 (16.67%) patients with insufficiency and 4 (10.00%) with sufficient vitamin D (p<0.001). Mean 25(OH)D concentrations decreased progressively with increasing severity in pediatric patients (24.36 ± 10.21, 18.92 ± 8.17, and 13.41 ± 6.82 ng/mL for mild, moderate, and severe ARI, respectively; p<0.001) and adults (25.18 ± 10.74, 19.74 ± 9.03, and 14.29 ± 7.16 ng/mL; p<0.001). Vitamin D deficiency was associated with severe ARI overall (OR=2.82, 95% CI: 1.48–5.39; p=0.002) and remained independently associated after adjustment (aOR=2.84, 95% CI: 1.43–5.64; p=0.003). Conclusion: Vitamin D deficiency was common and independently associated with greater severity of ARI among pediatric and adult patients.