Association of Vitamin D Deficiency With Cardiometabolic and Renal Outcomes in Patients With Autoimmune Rheumatic...

Autoimmune rheumatic diseases (ARDs) are chronic immune-mediated diseases associated with increased cardiovascular and renal morbidity. Vitamin D deficiency is common in these disorders and may coexist with inflammation, immune dysregulation, endothelial dysfunction, and impaired vascular and renal homeostasis. This systematic review and meta-analysis evaluated the association of vitamin D deficiency with adverse cardiometabolic and renal outcomes in ARDs. PubMed/MEDLINE, Scopus, Embase, Web of Science, and Google Scholar were searched from inception through March 31, 2026, without language restrictions. Observational studies that measured serum 25-hydroxyvitamin D (25(OH)D) and reported cardiometabolic, cardiovascular, renal, or cardiorenal outcomes were eligible. Two reviewers independently conducted study selection, data extraction, and quality assessment. Compatible outcome-specific estimates were pooled using constrained maximum-likelihood random-effects models with Hartung-Knapp inference. Hazard ratios (HRs) and correlation coefficients were examined independently. Eighteen studies met the eligibility criteria, and four independent cohorts contributed to at least one quantitative synthesis. Vitamin D deficiency was associated with higher all-cause mortality (pooled HR 1.95, 95% confidence interval (CI) 1.36-2.79). The pooled association with cardiovascular events was imprecise (HR 2.20, 95% CI 0.52-9.25). Serum 25(OH)D was inversely but inconclusively correlated with proteinuria in pediatric systemic lupus erythematosus (r = -0.47, 95% CI -0.98 to 0.85). Cardiometabolic studies generally reported adverse metabolic and vascular findings but could not be pooled because of incompatible effect measures. Vitamin D deficiency was associated with higher mortality and greater cardiometabolic and renal disease burden; however, cardiovascular-event and proteinuria estimates remained inconclusive. Observational designs, residual confounding, heterogeneous definitions, and few compatible studies precluded causal conclusions. Prospective studies and randomized trials are required to determine whether correcting vitamin D deficiency improves clinical outcomes.