Good glycemic control remains crucial in prevention of late diabetic complications – the Linköping Diabetes Complications Study

Background: Several intervention studies have convincingly demonstrated the importance of good glycemic control to avoid long-term diabetic complications, but the importance of other risk factors remains controversial. We previously reported a markedly reduced incidence of severe retinopathy and nephropathy during the past decades in an unselected population of type 1 diabetes mellitus diagnosed in childhood. The aim of the present study was to analyze possible risk factors, which could explain the improved prognosis.

Methods: In this longitudinal population-based cohort study, we followed all 269 patients in whom type 1 diabetes mellitus was diagnosed in childhood 1961–1985 in a well-defined geographical area in Sweden. The patients were followed until the end of 1990s. Multivariable regression models were used to analyze the importance of hemoglobin A1c (HbA_1c), diabetes duration, blood pressure, cardiovascular risk factors and persisting C-peptide secretion for the development of diabetic retinopathy and nephropathy.

Results: Beside longer duration and higher HbA_1c, blood pressure and lipid values were higher and cardiovascular disease and smoking were more common in patients with severe complications. However, multivariable analysis abolished these associations. Diabetes duration and long-term HbA_1c were the only significant independent risk factors for both retinopathy and nephropathy. The risk of overt nephropathy increased substantially when HbA_1c was above 9.6% [Diabetes Control and Complications Trial (DCCT) corrected value], while the risk of severe retinopathy increased already when HbA_1c exceeded 8.6%.

Conclusion: In this unselected population, glycemic control was the only significant risk factor for the development of long-term complications.