Protection from diabetic eye disease will decline

Compared with standard treatment, intensive control of type 1 diabetes can help stave off diabetic eye disease, but over time this benefit will decline, according to new data from the Epidemiology of Diabetes Interventions and Complications (EDIC) study.

Dr. David M. Nathan at Massachusetts General Hospital, Boston, and colleagues note in their report in the Archives of Ophthalmology that in the original Diabetes Control and Complications Trial (DCCT), "intensive therapy aimed at near-normal (blood sugar levels) reduced the risk of (diabetic eye disease or 'retinopathy') compared with conventional therapy."

At the end of the 6.5-year DCCT, average levels of HbA1c, a blood test of long-term sugar control, were almost normal in the intensive therapy group, but remained high in standard treatment group. At that point, patients returned to their usual health care providers and most were enrolled in the EDIC study, which simply followed them over time without being assigned to a specific treatment.

Soon after EDIC began, HbA1c values had begun to converge, and after 4 years they were no longer different in the groups that had been assigned intensive or standard therapy.

At 4 years, patients treated with intensive therapy were 74 percent less likely to develop retinopathy than those given standard therapy. By 10 years, however, the difference fell to 57 percent.

They stress that the persistence of benefit does not mean that intensive therapy need only be applied for a limited period. "Rather," they conclude, "the results support the implementation of intensive treatment as early in the course of the disease as possible." If aggressive blood sugar control is not maintained, however, the advantages are likely to diminish.

SOURCE: Archives of Ophthalmology, December 2008.