Vitamin D Deficiency and Associated Factors; An Observational Retrospective Study of 35,620 Vitamin D Levels

Abstract Objective Vitamin D deficiency represents a significant public health issue worldwide. In this study, the aim of this study was contribute to the existing literature on vitamin D prophylaxis practices by determining the prevalence of vitamin D deficiency among children and identifying the associated risk factors. Methods The 25-hydroxyvitamin D (25(OH)D) levels of 35,620 healthy children aged 0–18 years, who applied to the Pediatric Outpatient Clinic of Düzce University Faculty of Medicine, were retrospectively analyzed based on age groups, gender, seasons, and years. Results The mean serum 25(OH)D level was 21 ± 12.37 ng/mL (range: 3–99.8 ng/mL; median: 18.8 ng/mL). Serum 25(OH)D levels were ≤ 20 ng/mL in 19,484 patients (54.7%). Among these, 8099 patients (22.7%) were classified as having vitamin D deficiency, while 11,385 patients (32%) had vitamin D insufficiency. No statistically significant association was found between 25(OH)D levels or the prevalence of vitamin D deficiency and season, age groups, gender, or years. Conclusion Our study demonstrates that vitamin D deficiency is highly prevalent among children. To prevent this deficiency, it is essential to promote the consumption of foods containing vitamin D, ensure adequate and appropriate sunlight exposure, and implement routine prophylactic vitamin D supplementation for all children aged 0–18 years.