Risk of Developing Retinopathy in Diabetes Control and Complications Trial Type 1 Diabetic Patients With Good or Poor Metabolic Control

Abstract

OBJECTIVE—The study goal was to assess and predict the risk of developing retinopathy in type 1 diabetic patients with extreme metabolic control.

RESEARCH DESIGN AND METHODS—Based on material from the Diabetes Control and Complications Trial (DCCT) study (n = 1,441 patients), patients without retinopathy at baseline (DCCT primary cohort) were considered under good or poor metabolic control if the mean HbA_1c level (until the last visit) fell in the lower or upper 20% of the overall HbA_1c distribution, respectively. Retinopathy was recorded as either absent or present. Logistic regression was used to predict retinopathy from covariates used in the DCCT retinopathy study.

RESULTS—Among the 153 DCCT patients with “good metabolic control” (mean HbA_1c ≤6.87%), three-step change retinopathy developed in 15 (9.8%), and 138 (90%) remained free of retinopathy. Conversely, among the 166 patients with “poor metabolic control” (mean HbA_1c ≥9.49%), the complication did not develop in 71 (43%) and did develop in 95 (57%). Whereas occurrence of diabetic retinopathy was primarily due to metabolic control (P < 0.0001) and duration of participation in the study (P < 0.0001), two other covariates were found to be significant prognostic factors of the complication: HbA_1c at baseline (OR 1.37, P < 0.001) and BMI (OR 1.11, P < 0.05).

CONCLUSIONS—This study confirms that retinopathy develops in ∼10% of patients with type 1 diabetes under good metabolic control, whereas >40% of patients with type 1 diabetes remain free of retinopathy despite poor metabolic control. After adjusting for metabolic control and duration of participation in the study, it was found that previous glycemic exposure (HbA_1c) and BMI may provide a possible explanation to such paradoxical clinical situations.