Clinical and metabolic characteristics of type 1 and type 2 diabetes: an epidemiological study from the Närpes community in western Finland

Abstract

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.