Clinical and Metabolic Characteristics of Type 1 and Type 2 Diabetes: An Epidemiological Study From the Närpes Community in Western Finland

Clinical and metabolic characteristics of all known Type 1 and Type 2 diabetic patients in a well‐defined area in Western Finland are described. Retrospective data from the time of diagnosis and follow‐up data were examined. Overall prevalence of diabetes was 25.4 cases per 1000 population. Patients were defined as having Type 1 or Type 2 diabetes based upon early insulin requirement and C‐peptide levels. Applying these criteria 84% of the patients had Type 2 diabetes. Onset before the age of 40 years was observed in only 3% of Type 2 diabetic patients. This age limit therefore had a sensitivity of 97% and a specificity of 90% in correctly predicting Type 2 diabetes. At diagnosis, hypertension was observed in 2% of Type 1 and in 75% of Type 2 diabetic patients; the corresponding numbers at follow‐up were 6 and 63%. At investigation, 27% of Type 1 and 22% of Type 2 diabetic patients had microalbuminuria. Retinopathy was observed in only 12% of Type 2 compared with 54% of Type 1 diabetic patients. The presence of retinopathy was associated with longer diabetes duration both among Type 1 and Type 2 diabetic patients. A significant decrease in C‐peptide concentration was observed in Type 2 diabetic patients with increasing diabetes duration. The data therefore suggest that Type 2 diabetes is associated with a deterioration of beta‐cell function with time. 1992 Diabetes UK