Prediction of Retinopathy at 20 Years After Onset in Younger-Onset Type 1 Diabetes Using Mean Metabolic Memory-Free HbA1c Values

OBJECTIVE Metabolic memory, in which past hyperglycemia could affect future retinopathy, is a potential issue in studying the relationship between glycemia and retinopathy. We examined retrospectively if mean "metabolic memory-free" glycosylated hemoglobin A1C (HbA1c) values covering total diabetes duration could predict retinopathy in younger-onset type 1 diabetes mellitus (T1DM). RESEARCH DESIGN AND METHODS Inclusion criteria were T1DM onset before age 30 years, first visit to our center between 1988 and 1990 soon after onset, continuous HbA1c data for 20 years, and a 20-year follow-up retinopathy examination. Retinopathy predictive capabilities of HbA1c variables were examined. RESULTS Of 15 subjects, 5 were retinopathy-positive and 10 were retinopathy-negative at the 20-year follow-up. Mean metabolic memory-free HbA1c values for the 20 years showed a substantial capacity to predict retinopathy at 20 years. The longer the period without HbA1c data following onset in simulation, the less accurate the prediction. CONCLUSIONS HbA1c values may predict retinopathy better if metabolic memory-free data are used.