Patients with diabetic retinopathy are more likely to have lower 25-hydroxyvitamin D levels vs. healthy controls, according to a speaker here.

“Vitamin D may have a role in the pathophysiology of creating diabetic retinopathy,” Anawin Sanguankeo, MD, of the department of medicine at Bassett Medical Center in Cooperstown, New York, said during a media briefing at the AACE Scientific and Clinical Congress. “In the future, there should be studies that assess [whether] giving vitamin D to patients that have diabetes will prevent diabetic retinopathy or slow progression in patients who already have [diabetic retinopathy] compared to patients who do not have optimal vitamin D.”

Vitamin D deficiency, Sanguankeo said, has been associated with several cardiometabolic complications, including insulin secretion, metabolic syndrome and systemic diabetes progression. The role of vitamin D in the pathogenesis of diabetic retinopathy in humans remains an area of debate, though studies in rat models suggest an association, he said.

Sanguankeo, Sikarin Upala, MD, also of Bassett Medical Center, and colleagues completed a systematic review and meta-analysis of 11 observational studies conducted through July 2015, assessing the relationship between vitamin D deficiency (serum 25-(OH)D 20 ng/mL or less) and diabetic retinopathy (n = 9,350). Researchers calculated the pooled effect estimate of diabetic retinopathy, comparing patients with optimal vitamin D levels and vitamin D-deficient groups, and calculated the pooled mean difference of 25(OH)D levels between patients with diabetic retinopathy and healthy controls, using a random-effect, Mantel-Haenszel analysis.

Researchers found an association between diabetic retinopathy and vitamin D deficiency (OR = 1.27; 95% CI, 1.17-1.37). In patient subgroups, researchers also found that patients with diabetic retinopathy had lower serum 25-(OH)D levels vs. controls, with a mean difference of –2.22 ng/mL; 95% CI, –2.78 to –1.67).

“I think that evidence is strong enough to have future studies in this area,” Sanguankeo said. “Before there is a recommendation for clinicians [ to supplement with vitamin D], there should be evidence stronger than this, in randomized controlled trials or in prospective cohort studies. This is just the beginning of future studies that should be done.”