Association between serum vitamin D levels and the risk of diabetic retinopathy: a meta-analysis

Aim: This meta-analysis was conducted to quantitatively synthesize existing evidence on the relationship between serum 25-hydroxyvitamin D [25(OH)D] levels and diabetic retinopathy (DR). Methods: A systematic search of PubMed, Embase, the Web of Science, and the Cochrane Library was performed for obtaining observational studies published between January 2015 and February 2026. The included studies reported adjusted effect estimates for the association between 25(OH)D levels and DR. A random-effects model was used to calculate pooled odds ratios (ORs) with 95% confidence intervals (CIs). Subgroup analysis was performed to explore the sources of heterogeneity based on ethnicity, diabetes type, study design, and vitamin D assay method. A sensitivity analysis was conducted to evaluate the robustness of the pooled results. Publication bias was assessed using Begg's funnel plot and Egger's linear regression test. Results: This meta-analysis included 16 relevant studies, and the pooled results showed that low serum vitamin D levels were associated with a higher likelihood of developing DR (OR = 1.87, 95% CI: 1.66-2.11). Subgroup analyses revealed stronger effect sizes in Asian populations (OR = 1.97, 95% CI: 1.63-2.38) and type 1 diabetes mellitus (T1DM) patients (OR = 2.15, 95% CI: 1.70-2.72). The sensitivity analysis confirmed the robustness of the findings, and publication bias was not observed. Conclusion: Low vitamin D levels were associated with higher odds of developing DR, and this association was particularly evident in Asian individuals and T1DM patients. These findings suggest the importance of monitoring vitamin D levels in the management of DR.