Determinants of retinopathy progression in type 1 diabetes mellitus

PURPOSE: To determine the risk factors for retinopathy progression in type 1 (insulin-dependent) diabetes mellitus in a prospective cohort study. SUBJECTS AND METHODS: Subjects were 485 participants in the Sorbinil Retino pathy Trial, a randomized trial of aldose reductase inhibition among patien ts aged 18 to 56 years with type 1 diabetes mellitus (duration of 1 to 15 y ears) and no or only mild retinopathy. Retinopathy progression, assessed by seven-field stereoscopic fundus photography, was defined as worsening by t wo or more levels on a standardized grading scale at the end of follow-up ( median, 41 months). RESULTS: The relative risks for retinopathy progression according to succes sively greater quintiles of total glycosylated hemoglobin level at baseline , after adjusting for age, diabetes duration, sorbinil assignment, and othe r variables, were 1.0, 2.0, 1.6, 3.7, and 4.4 (P trend <0.0001). Risk incre ased with greater baseline diastolic blood pressure: 1.0 for <70 mm Hg, 1.2 for 70 to 79 mm Hg, and 1.8 for greater than or equal to 80 mm Hg (P for t rend = 0.04). Diastolic blood pressure was a significant risk factor for pr ogression in participants with mild baseline retinopathy (P for trend <0.02 ) but not in those without retinopathy at entry. Systolic blood pressure, b y comparison, was not associated with progression. Baseline total cholester ol level was a marginally significant predictor of retinopathy progression when examined as a categorical variable (relative risks for increasing quar tiles; 1.0, 1.6, 1.8, 1.9; P for trend = 0.03) but not when it was examined as a continuous variable or when hypercholesterolemic patients were compar ed with those with normal levels. Furthermore, when cholesterol levels were updated in subsequent visits, it was not a significant predictor of progre ssion, and low density lipoprotein (LDL) cholesterol levels did not predict progression no matter how analyzed. Smoking was not associated with progre ssion of retinopathy. CONCLUSIONS: Levels of hyperglycemia and diastolic blood pressure predicted progression of retinopathy in type 1 diabetes mellitus. We found only a su ggestion of an association between total cholesterol level (but not of LDL cholesterol level) and progression of retinopathy; resolution of this issue will require additional studies with larger sample sizes and longer follow -up. (C) 1999 by Excerpta Medica, Inc.