Nahide HAYKIR, Yasemin AKIN, Engin TUTAR
Southern Clinics of Istanbul Eurasia - 2026;37(3):224-229
Objective: This study aimed to evaluate serum 25-hydroxyvitamin D [25(OH)D] levels in children aged 0-5 years presenting with lower respiratory tract infection (LRTI) and to investigate the association between vitamin D deficiency and infection severity. Methods: In this prospective controlled study, a total of 100 children aged 0-5 years were enrolled. The study group consisted of patients diagnosed with LRTI, while the control group included healthy children. Serum 25(OH)D, calcium, phosphorus, alkaline phosphatase (ALP), C-reactive protein (CRP), and complete blood count parameters were measured in all participants. Vitamin D status was classified as severe deficiency, deficiency, insufficiency, or normal. Statistical significance was set at p<0.05. Results: Children diagnosed with LRTI had significantly lower serum 25(OH)D levels compared to the control group (p<0.001). CRP and leukocyte levels were significantly higher in the study group (p<0.001). A significant association was observed between vitamin D deficiency and frequent infections as well as hospitalization rates. Inflammatory markers were higher in the severe vitamin D deficiency group. Additionally, serum 25(OH)D levels decreased with increasing age (p<0.001). Conclusions: Low serum 25(OH)D levels appear to be associated with increased frequency and severity of lower respiratory tract infections in early childhood. Early detection of vitamin D deficiency and maintenance of appropriate supplementation strategies may represent an important preventive approach to reducing infection burden.
