10–Year Retinopathy Outcomes in the EDIC Cohort: Effect of the Original DCCT Treatment Group Assignment

Abstract

Abstract: : Purpose: The Diabetes Control and Complications Trial (DCCT) (1982–1993) demonstrated lessening of the development and progression of retinopathy, nephropathy, and neuropathy in patients with type 1 diabetes randomly assigned to intensive therapy (with the aim of achieving near–normal glycemic control) as compared to conventional therapy. To assess the degree to which the reduction in progression of retinopathy persists, photographic grading was performed at the 10 year time point following the end of the randomized trial. Methods: At the end of the DCCT, the patients in the conventional therapy group were taught intensive therapy, and the care of patients was transferred to their own physicians. 1373 of the original 1441 DCCT patients were enrolled in the Epidemiology of Diabetes Interventions and Complications (EDIC) study. Of these, 1189 had retinopathy assessment at year 10 post DCCT (mean follow up 16 years from baseline). ETDRS seven standard field stereoscopic color photographs were obtained on all patients at baseline, at approximately year 4, and year 10 and graded at a central reading center. Progression of retinopathy was defined as 3 or more steps worsening on the ETDRS scale. Results: The difference in glycohemoglobin levels between former DCCT groups, 7.2% in the intensive treatment group (IT) and 9.1% in the conventional treatment group (CT), narrowed to 8.0% vs. 8.1%, respectively. Nevertheless, the risk reduction in the former IT group for 3–step progression was 52% (P < 0.0001, adjusted Weibull Model). There was no evidence of a plateau or lessening of the risk reduction over time. The proportion of patients with proliferative retinopathy, macular edema, and the need for laser treatment was reduced in the IT versus CT groups as well (p<0.001, Fisher’s exact test). Conclusions: The reduction in risk of progressive retinopathy resulting from intensive therapy in patients with type 1 diabetes persists for at least 10 years, despite marked narrowing of the glycosylated hemoglobin difference between the former DCCT treatment groups.

Keywords: diabetic retinopathy • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled • clinical (human) or epidemiologic studies: outcomes/complications