Prevalence of Vitamin D Deficiency in Children and Adolescents With Type 1 Diabetes Mellitus: A Systematic Review and Meta-Analysis.

Our systematic review and meta-analysis examined the proportion of vitamin D deficiency in children and adolescents with type 1 diabetes mellitus (T1DM). We conducted a comprehensive literature search across multiple databases, including PubMed, Cochrane Library, Web of Science, Ovid Medline, and Embase, for studies published between January 2016 and March 2025. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, 29 studies comprising 2516 participants were included in the final analysis. Quality assessment was performed using the Newcastle-Ottawa Scale. The pooled analysis revealed that 46% (95% CI: 34-58%) of children and adolescents with T1DM had vitamin D deficiency, with significant heterogeneity observed across studies (I² = 97.98%, p<0.01). Subgroup analysis showed geographical variations with the highest deficiency rates in Africa (74%). The definition of vitamin D deficiency also impacted results, with cutoffs of <25 ng/mL yielding the highest proportion (80%) and <12 ng/mL the lowest (14%). Despite methodological limitations, including clinical setting bias, varied study designs, and inconsistent deficiency thresholds, our findings highlight the substantial burden of vitamin D deficiency in pediatric T1DM patients. This suggests the need for routine screening and potential supplementation strategies, though further research is required to establish optimal vitamin D levels for T1DM management and determine whether supplementation could play a preventive or therapeutic role in this population.