Objective
To assess the relationship between vitamin D status and diabetic retinopathy
Methods
A clinic-based, cross-sectional study was conducted at Emory University. A total of 221 subjects were classified into five 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 (No BDR; n = 41), nonproliferative diabetic retinopathy (NPDR; n = 40), and proliferative diabetic retinopathy (PDR; n = 42). Key exclusion criteria included type 1 diabetes and those taking > 1000 IU vitamin D daily. Subjects underwent dilated fundoscopic examination and were tested for hemoglobin A1c, serum creatinine, and 25-hydroxy-vitamin D (25(OH)D) between December 2009 and March 2010.
Results
Between the groups, there was no statistical difference in age, race, sex, or multivitamin use. Diabetic subjects had lower 25(OH)D levels than non-diabetic subjects (22.9 ng/ml versus 30.3 ng/ml, p<0.001). The mean 25(OH)D levels were as follows: No diabetes or ocular disease = 31.9 ng/ml, No diabetes with ocular disease = 28.8 ng/ml, No BDR = 24.3 ng/ml, NPDR = 23.6 ng/ml, PDR = 21.1 ng/ml. Univariate analysis of the 25(OH)D levels demonstrated statistical significance between the study groups, race, body mass index, multivitamin use, hemoglobin A1c, serum creatinine, and estimated glomerular filtration rate. In a multivariate linear model with all potential confounders, only multivitamin use remained significant (p<0.001).
Conclusions
This study suggests that diabetic subjects, especially those with PDR, have lower 25(OH)D levels than those without diabetes.
