The prevalence of retinopathy in subjects with and without type 2 diabetes mellitus

Purpose:  To evaluate the prevalence of and risk factors for, retinopathy in a geographically defined population with type 2 diabetes mellitus compared with a control group of subjects without diabetes, matched by age, sex and residence in order to find the retinopathy attributable to type 2 diabetes. Methods:  The study populations are, on one hand, a prevalence cohort of subjects with type 2 diabetes resident in the community of Laxå, Sweden, and on the other a control group, matched by age, gender and residence with those with a diagnosis of type 2 diabetes mellitus. Retinopathy was graded from fundus photographs using a modification of the Early Treatment Retinopathy Study (ETDRS) adaptation of the modified Airlie House classification of diabetic retinopathy (DR). Results:  Any retinopathy was found in 34.6% in the type 2 diabetes cohort and in 8.8% in the control group without diabetes. Among the diabetic patients, any retinopathy was significantly associated with duration of diabetes (p = 0.0001), HbA1c (p = 0.0056), systolic blood pressure (p = 0.0091) and lower serum cholesterol (p = 0.0197) in multivariate logistic regression analyses. Having retinopathy in the control group was associated only with systolic blood pressure (p = 0.0014) in logistic regression analysis. Conclusions:  The prevalence of retinopathy among patients with type 2 diabetes in Laxå, Sweden, was similar or somewhat lower compared with other studies in the Nordic countries. The prevalence of retinopathy in a control group without diabetes equalled numbers from population studies worldwide. Our study indicates that the retinopathy that can be attributed to hyperglycaemia in the diabetic state is less common than is usually accounted for. A considerable fraction of retinopathy in subjects with diabetes may instead be due to other factors such as hypertension and should thus be treated correspondingly.