Vitamin D and retinopathy in adults with diabetes

ABSTRACT

OBJECTIVE. Retinopathy is one of the most frequent complications of diabetes in adults. Results from animal studies have suggested that vitamin D may protect the diabetic retina. Given the possible protective effect of vitamin D on vascular health and the prevalence of inadequate vitamin D levels in adults, the hypothesized association between vitamin D inadequacy and diabetic retinopathy was explored.

RESEARCH DESIGN AND METHODS. This question was investigated by examining data from individuals aged 40 years and older with diabetes who participated in the interview and medical examination components of the National Health and Nutrition Examination Survey conducted from October 1988 through October 1994 (“NHANES III”).

RESULTS. A total of 1790 NHANES participants met the study's inclusion criteria. The proportion of subjects with vitamin D deficiency (25-OHD <20 ng/ml) increased with increasing severity of retinopathy: 27.9%, no retinopathy (n=1522); 28.2%, mild (n=168); 43.2%, moderate/severe (n=88); and, 64.6%, proliferative (n=12) (adjusted for age and obesity, p=0.01). Median vitamin D levels by retinopathy severity score were as follows: 25.8 ng/ml, no retinopathy; 26.6 ng/ml, mild; 21.5 ng/ml, moderate/severe; 13.6 ng/ml, proliferative (unadjusted, p=0.07; adjusted for age and obesity, p=0.13).

CONCLUSIONS. Results suggest an inverse relationship between the severity of diabetic retinopathy and serum vitamin D levels. Given previous evidence suggesting possible anti-angiogenic properties of vitamin D and the small number of subjects in this sample with proliferative retinopathy, this last finding warrants further study.