Prolonged Effect of Intensive Therapy on the Risk of Retinopathy Complications in Patients With Type 1 Diabetes Mellitus

Abstract

The Diabetes Control and Complications Trial (DCCT) was designed to determine whether intensive therapy with the aim of maintaining glycemic levels as close to the nondiabetic range as possible would prevent or delay the long-term complications of type 1 diabetes mellitus.¹The DCCT demonstrated substantial reductions in the risk of development and progression of the early microvascular complications of diabetes over an average of 6.5 years of intensive therapy as compared with conventional therapy. At the close of the DCCT in 1993, patients in the conventional therapy group were offered intensive therapy and instructed in its use. All patients subsequently returned to their health care providers for further diabetes care and 97% of the original DCCT cohort (n = 1394) was enrolled in the Epidemiology of Diabetes Interventions and Complications (EDIC), a long-term observational study.²An earlier report showed that the ongoing risk of all levels of retinopathy remained significantly reduced in the intensive compared with the conventional group during the first 4 years of EDIC, despite similar glycated hemoglobin (HbA_1c) levels over this period (called “metabolic memory”).³Determining the duration of metabolic memory is important to quantify the long-term clinical effects of intensive diabetes therapy. The current report describes the continuing differences between the 2 original treatment groups in retinal complications 10 years after the close of the DCCT.