Reduced vitamin D levels in diabetic retinopathy: cause or effect?

Abstract

Aims: Research suggests that vitamin Ddeficiency is associated with diabetic retinopathy (DR). Our study aimed to understand whether vitamin D deficiency is the cause of DR or whether people with DR have low vitamin D. Methods: Participants with type 2 diabetes were recruited for this prospective observational clinical study and were divided into a diabetic group without retinopathy and a diabetic group with retinopathy, with additional healthy volunteers serving as controls. The differences in clinical characteristics between the three groups were compared. The incidence of DR in patients without retinopathy was then followed for one year. Follow-up participants were divided into subgroups based on whether DR occurred. Baseline data of subgroups were compared, and independent risk factors were analyzed. Results: Vitamin D levels were generally low. Participants with DR had significantly lower vitamin D levels than those without retinopathy (P< 0.01). A comparison of the two subgroups revealed lower baseline vitamin D data in the new-DR subgroup than in the non-DR subgroup (P< 0.01). Vitamin D deficiency and elevated HbA1c levels were independent risk factors for DR (OR= 0.926, 95% CI: 0.867～0.990, P= 0.024; OR= 2.108, 95% CI: 1.540～2.883, P< 0.01). The limit of vitamin D measured using the ROC curve was 18.15 ng/mL, and the area under the ROC curve was 0.635 (95% CI: 0.559～0.706, P= 0.002). Conclusions: Vitamin D levels were significantly reduced in those diagnosed with DR. At the same time, vitamin D deficiency may accelerate the onset of DR.