Diabetic retinopathy linked to higher risk of stroke

Damage to small blood vessels of the eye appears to be a significant marker for an increased risk of stroke in patients with diabetes, suggesting that the microvascular pathology inherent to diabetic retinopathy may have greater cardiovascular implications, according to a study presented at the American Stroke Association’s (ASA) International Stroke Conference (ISC) 2020 in Los Angeles, US.

“A build-up of plaque in large arteries feeding the brain and the common heart arrhythmia atrial fibrillation are the primary causes of ischaemic strokes, and damage to small blood vessels also cause stroke and vascular dementia, so we thought that diabetic retinopathy might be an important biomarker of stroke risk for patients with diabetes,” said Ka-Ho Wong, lead author and clinical research coordinator and lab manager of the de Havenon Lab at the University of Utah Health Hospitals and Clinics in Salt Lake City, Utah, in a press statement by ASA.

Wong and colleagues conducted a secondary analysis of the subgroup of patients enrolled in the ACCORD Eye Study. Stroke during follow-up was the primary outcome. The primary predictor was the presence of diabetic retinopathy on the Early Treatment Diabetic Retinopathy Study Severity Scale as assessed from seven-field stereoscopic fundus photographs at baseline. Adjusted Cox models were fit to the primary outcome to estimate hazard ratios (HRs) for stroke.

Of the 2,828 patients (mean age, 62.1 years; 61.8 percent male) included in the study, 117 had suffered stroke during a mean follow-up of 5.4 years. At baseline, 874 patients (30.9 percent) presented with diabetic retinopathy, which appeared to be more common in patients with stroke compared with those without (41.0 percent vs 30.5 percent; p=0.016). [ISC 2020, abstract 154]

The association between diabetic retinopathy and incident stroke (HR, 1.60, 95 percent confidence interval [CI], 1.10–2.32; p=0.015) persisted in the Cox model, adjusted for baseline patient age, gender, race, total cholesterol, glycated haemoglobin, smoking and randomization arm. This association was not influenced by randomization to the ACCORD glucose intervention (p=0.305), lipid intervention (p=0.546) or blood pressure intervention (p=0.422).

“We were surprised that none of the ACCORD interventions decreased diabetic retinopathy and stroke risk, especially intense blood-pressure reduction, since a lot of microvascular diseases are caused by high blood pressure,” Wong said in a statement. “This finding is in line with results from ACCORD, which showed no reduction in heart attacks.”

Despite these findings, patients with diabetic retinopathy were advised to receive “aggressive medical management” to lower the risk of stroke, according to the researchers.

The ASA recommends the following to reduce the risk of stroke: healthy lifestyle, including low salt intake; regular physical activity; healthy weight; tobacco avoidance; stress management; limited alcohol intake (<1 drink per day for women and 2 drinks per day for men); and adherence to medication as prescribed for high blood pressure, diabetes, high cholesterol and atrial fibrillation.

“Diabetic retinopathy is a common microvascular complication of diabetes,” the researchers said. “Previous research has shown that the macrovascular complications of diabetes, including stroke, are often comorbid with shared and, possibly, synergistic pathology.”