Effect of Diabetic Control on the Development of Retinopathy in Non-Insulin-Dependent Diabetes Mellitus

Prospective Follow-up Study for 8 years

Abstract

To determine the optimum (HbA_1c) value for preventing retinopathy, the progression of retinopathy and HbA_1c values in patients with non-insulin-dependent diabetes mellitus (NIDDM) were followed for 8 years. We examined 176 patients first diagnosed with NIDDM, aged 30-65 years, diabetic duration less than 3 years and without retinopathy. The appearance and progression of retinopathy were assessed at least annually. The mean HbA_1c value for each patient was calculated by using data of every month except the data at registration. Multiple logistic regression analysis for the mean HbA1c value, onset age, sex, blood pressure, and ΔBMI (Max BMI-BMI at registration) with retinopathy at the end point as dependent variables, showed a significant impact of the mean HbA_1c value and ΔBMI. In the group with HbA_1c values below 6%, no patients had retinopathy. Patients with HbA_1c values above 8% had a prevalence rate 4 times higher than patients with HbA_1c values below 8%. The prevalence of retinopathy increased with the increase in the mean HbA_1c values over 8 years (trend P<0.05). The data suggest that an HbA_1c value below 6% should be effective in preventing diabetic retinopathy in patients with NIDDM.