Objective: To describe the long-term simultaneous impacts of blood pressure and glycosylated haemoglobin values on the risk of progression of diabetic nephropathy.
Design: Prospective, multicentre, 6-year follow-up study.
Setting: One reference centre (university department of internal medicine) and nine general hospitals.
Subjects: A total of 601 type 1 diabetic patients on intensive insulin therapy with and without diabetic nephropathy.
Main outcome measures: Progression of nephropathy was defined as change for the worse within five stages of nephropathy by at least one of these stages during the study period. By the use of logistic regression, the relationship between metabolic and blood pressure control and the risk of nephropathy progression was quantified.
Results: The main determinants of nephropathy progression were glycosylated haemoglobin and blood pressure, which were both non-linearly associated with the risk of progression. No significant threshold levels for any of the predictors of progression were identified.
Conclusions: The results of this study underline the importance of optimizing metabolic and blood pressure control to arrest the progression of diabetic nephropathy without the evidence for a clinically relevant threshold effect.