Retinopathy Linked to Vitamin D Deficiency – MedPage Today
ORLANDO – Diabetic patients who have also been diagnosed with vitamin D deficiency may be at risk of developing diabetic retinopathy, researchers reported here.
In a meta-analysis that included 11 publications and involved studies that included about 6,000 individuals, diabetic patients with vitamin D deficiency were 26.7% more likely to have diabetic retinopathy than patients who were not deficient in the so-called sunshine vitamin (OR 1.267 [95% CI 1.168-1.373, P<0.001]), said Anawin Sanguankeo, MD, a resident in medicine at Bassett Medical Center, Cooperstown, N.Y.
At a press conference during the annual meeting of the American Association of Clinical Endocrinologists, Sanguankeo told MedPage Today: “Our meta-analysis of large observational studies demonstrated a significant association between vitamin D deficiency and diabetic retinopathy, as well as a quantifiable statistically significant difference in mean serum vitamin D levels between patients with diabetic retinopathy and control patients.”
There was a statistically significant lower serum 25-hydroxyvitamin D level in patient subgroups with diabetic retinopathy compared with control groups, with a mean difference of -2.25 ng/mL (95% CI: -3.64 to -0.87, P=0.001), he reported.
Sanguankeo said that even though the results could not show a cause-and-effect relationship, “I think that patients who have diabetes and low vitamin D need to have eye examinations to see if they have diabetic retinopathy, because they may be at higher risk than people without a deficiency.”
However, he cautioned, “our findings are from retrospective studies. We need a prospective randomized controlled trial to see if vitamin D deficiency really has a cause-and-effect relationship with diabetic retinopathy.”
To perform the study, he and his colleagues, searched MEDLINE and Embase for published studies from their date of inception to July 2015. “We conducted a systematic review and meta-analysis of observational studies that assessed the association between diabetic retinopathy and vitamin D deficiency,” Sanguankeo said, adding that for the purpose of the study, vitamin D deficiency was defined as a serum level less than 20 ng/mL; optimal vitamin D level was defined as a serum level greater than 30 ng/mL.
The researchers eventually found 122 articles that satisfied the search terms, but all but 26 were eliminated because they were not full-text. After further exclusion, 11 articles were left for the analysis. All the papers selected for the analysis were published since 2012. The papers selected included adults who were diagnosed with either type 1 diabetes or type 2 diabetes mellitus, and the patients had to also have had their serum vitamin D measured.
“This study represents the first meta-analysis and systemic review analyzing the association between diabetic retinopathy and vitamin D deficiency in the English language literature,” Sanguankeo said. “The role of vitamin D in cellular inflammation pathways, endothelial cell proliferation, and angiogenesis is well established, but the role in diabetic retinopathy has to date been obscured in clinical trials by disease pathogenesis, varied diabetic retinopathy classifications, and differing patient ethnic populations.
“Future researchers should try to determine if vitamin D supplementation has a clinical benefit and consider if vitamin D supplementation is a protective mechanism against the development and progression of diabetic retinopathy.”
Commenting on the study, Reid Litchfield, MD, a private practitioner and researcher in Henderson, Nev., told MedPage Today at the press conference: “There are hypothesis-generating observational studies, but this is a first look to see if there is a potential link between two very prevalent conditions — the presence of retinopathy in diabetes and vitamin D deficiency.
“We live more and more inside, and when we are outside we are covered with sunscreens and hats and sun-protective clothing, so even in a sunny place like Las Vegas we see quite a bit of vitamin D deficiency,” he said.
“The study is provocative and interesting and should be the basis for further work and investigation.”
Sanguankeo reported no relevant relationships with industry. Litchfield disclosed relationships with Novo Nordisk.
Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco