Intensive control of blood sugar levels can cut the risk of diabetic retinopathy in half, according to a follow-up study of the landmark ACCORD (Action to Control Cardiovascular Risk in Diabetes) trial.
The finding from the ACCORD Follow-on eye study (ACCORDION) “sends a powerful message to people with type 2 diabetes mellitus (T2DM) who worry about losing vision,” said Emily Chew, MD, deputy director of the National Eye Institute Division of Epidemiology and Clinical Applications and lead author of the study report.
The ACCORDION trial is an assessment of diabetic retinopathy progression in 1,310 people who participated in ACCORD. That study tested 3 treatment strategies to reduce the risk of cardiovascular disease in people with longstanding T2DM: maintaining near-normal blood sugar levels (intensive control), improving blood lipid levels, and lowering blood pressure.
Because of an increase in death among participants in the intensive glycemic control group, ACCORD was aborted at 3.5 years. (The increased mortality, which was due to a range of causes, was seen in both intensive and standard groups.) From the data they had, the researchers found tight control reduced glycemia to an average HbA1C of 6.4% compared with 7.7% among those in the standard control group. It did not cut the risk of cardiovascular disease, but it had cut retinopathy progression by about one- third when the study was abruptly ended.
The follow-up study reassessed diabetic retinopathy 4 years after the intensive control portion of ACCORD had ended, 8 years after enrollment. Average HbA1C was nearly the same. Diabetic retinopathy, however, had advanced in only 5.8% of participants in the intensive group, compared with 12.7% of the standard treatment group.
The continuing beneficial effects—an approximately 50% reduction in risk of further retinopathy progression—are attributed to “metabolic memory,” a phenomenon also known as the “legacy effect.” Similar effects have been seen in 2 other large, long studies: the 10-year-long Diabetes Control and Complications Trial and the United Kingdom Prospective Diabetes Project.