Vitamin D insufficiency in diabetic retinopathy

To assess the relationship between vitamin D status and diabetic retinopathy.

A clinic-based, cross-sectional study was conducted at Emory University, Atlanta, Georgia. Overall, 221 patients were classified into 5 groups based on diabetes status and retinopathy findings: no diabetes or ocular disease (n = 47), no diabetes with ocular disease (n = 51), diabetes with no background diabetic retinopathy (n = 41), nonproliferative diabetic retinopathy (n = 40), and proliferative diabetic retinopathy (PDR) (n = 42). Patients with type 1 diabetes and those taking >1,000 IU of vitamin D daily were excluded from the analyses. Study subjects underwent dilated funduscopic examination and were tested for hemoglobin A1c, serum creatinine, and 25-hydroxyvitamin D [25(OH)D] levels between December 2009 and March 2010.

Among the study groups, there was no statistically significant difference in age, race, sex, or multivitamin use. Patients with diabetes had lower 25(OH)D levels than did those without diabetes (22.9 ng/mL versus 30.3 ng/mL, respectively; P<.001). The mean 25(OH)D levels, stratified by group, were as follows: no diabetes or ocular disease = 31.9 ng/mL; no diabetes with ocular disease = 28.8 ng/mL; no background diabetic retinopathy = 24.3 ng/mL; nonproliferative diabetic retinopathy = 23.6 ng/mL; and PDR = 21.1 ng/mL. Univariate analysis of the 25(OH)D levels demonstrated statistically significant differences on the basis of study groups, race, body mass index, multivitamin use, hemoglobin A1c, serum creatinine level, and estimated glomerular filtration rate. In a multivariate linear regression model with all potential confounders, only multivitamin use remained significant (P<.001).

This study suggests that patients with diabetes, especially those with PDR, have lower 25(OH)D levels than those without diabetes.