Spotlight on diabetic retinopathy

Multiple recent studies investigated associations between diabetic retinopathy and drugs, other diseases, and outcomes.

In the first study, published by Diabetes Care on July 30, incidence of age-related macular degeneration was compared among patients with and without diabetes and diabetic retinopathy. The retrospective study included 54,616 Taiwanese patients ages 50 years or older. It found a nonsignificant trend toward higher rates of age-related macular degeneration among patients with diabetes compared to those without. But among patients with diabetes, those with diabetic retinopathy had significantly higher risk of exudative and nonexudative age-related macular degeneration. Whether patients with diabetic retinopathy had proliferative or nonproliferative disease did not have a significant impact on risk of age-related macular degeneration. The study authors noted that the relationship between diabetic retinopathy and age-related macular degeneration has been poorly understood and that research on the relationship between diabetes and age-related macular degeneration has found contradictory results. “Our results revealed that patients with diabetes had a tendency toward a greater risk of nonexudative and exudative [age-related macular degeneration] than the matched control subjects. This trend was intensified when [diabetic retinopathy] developed in these patients with diabetes,” the authors said. This suggests that diabetic retinopathy and age-related macular degeneration may share pathogenic features and that preventing diabetic retinopathy in patients with diabetes may reduce risk of age-related macular degeneration, they noted. The study was limited by a number of factors, including its use of administrative data and uncertain generalizability to non-Taiwanese populations.

The second study, published by BMJ Open on July 25, also used data from Taiwan to examine the mortality risk associated with diabetic retinopathy and chronic kidney disease with normal urinary albumin or protein (NA-CKD). The retrospective study included 665 patients with type 2 diabetes who were hospitalized due to poor glucose control. Those with urinary protein excretion over 150 mg/d or urine albumin excretion over 30 mg/d were excluded. Over a median follow-up of 6.7 years, the patients with NA-CKD and diabetic retinopathy had the highest mortality rate, with significantly greater adjusted risk for both all-cause mortality and cardiovascular mortality than patients with only one or neither condition. The authors noted that widespread use of renin-angiotensin-aldosterone system inhibitors has led to NA-CKD being found in the majority of patients with diabetic kidney disease. The results suggest that screening for diabetic retinopathy and NA-CKD may help identify patients at high risk of dying, the authors said.

The third study, published by Diabetes Care on July 16 and supported by a pharmaceutical grant, compared rates of diabetic retinopathy among older U.S. patients taking different diabetes drugs. It included 213,652 fee-for-service Medicare beneficiaries covered between 2007 and 2015. The primary outcome was advanced diabetic retinopathy requiring treatment. The authors grouped patients without prior treatment for retinopathy by the medications they took: dipeptidyl peptidase 4 (DPP-4) inhibitors were compared to sulfonylureas and thiazolidinediones, while glucagon-like peptide 1 (GLP-1) receptor agonists were compared to long-acting insulin and thiazolidinediones. Over a median follow-up of less than a year, the adjusted hazard ratios for advanced diabetic retinopathy were 0.91 (95% CI, 0.79 to 1.04) and 0.91 (95% CI, 0.75 to 1.11) for DPP-4 inhibitors compared to sulfonylureas and thiazolidinediones, respectively, and 0.50 (95% CI, 0.39 to 0.65) and 0.75 (95% CI, 0.53 to 1.06) for GLP-1 receptor agonists compared to insulin and thiazolidinediones, respectively. The authors concluded that the use of incretin-based therapies for about a year was not associated with increased risk of diabetic retinopathy. They noted their data was primarily based on exenatide and liraglutide, as well as some albiglutide and dulaglutide. The study did not include semaglutide, which previous research has suggested might have an association with diabetic retinopathy. The study had several limitations, including a population of solely elderly Medicare patients, short follow-up, and lack of information on duration of diabetes or glycemic control.