Risk of diabetic retinopathy halved by intensive blood sugar lowering
Intensive therapy to lower blood sugar levels more than halves the risk of diabetic retinopathy in type 2 diabetes, a US study has found.
“This study sends a powerful message to people with type 2 diabetes who worry about losing vision,” says lead author Dr Emily Chew of the Washington-based National Eye Institute.
The findings come from an analysis of the ACCORD study, which looked at cardiovascular outcomes in 1300 type 2 patients assigned to one of 3 groups comprising tight glycaemic (blood sugar) control, improving lipid levels or lowering blood pressure.
The tight blood sugar control arm was stopped early, after three and a half years, due to an increase in death compared with the other arms. However, the researchers noticed that the therapy had reduced retinopathy progression by around a third.
Four years after treatment was stopped, they looked at retinopathy rates again and found diabetic retinopathy had advanced in only 5.8% of those in the intensive therapy arm, compared with 12.7% in the other arms.
This was despite the fact that, by now, HbA1C, a measure of blood glucose control over time, was virtually the same across groups (7.8% vs 7.9%).
The researchers say this effect is known as “metabolic memory” or the “legacy effect”.
It has previously been shown in a UK trial with type 1 patients, who received intensive glycaemic therapy and who had 50% less progression of retinopathy 3 decades later.
Patients in the current trial had had diabetes for an average of 10 years, with initial mean HbA1C of 8.2%.
“These observations suggest that glucose lowering can reduce progression of retinal disease relatively late in the course of diabetes and that the retina responds to relative short-term changes in glucose levels,” the researchers write.
They add that the benefits of intensive glycaemic therapy must be balanced against potential risks, including greater risk of death as observed in the ACCORD study.
The study was presented this week at the American Diabetes Association annual meeting in New Orleans and simultaneously published in the journal Diabetes Care.