Aims/hypothesis: It is not known whether mean blood glucose (MBG) predicts the risk of macrovascular complications in diabetes any differently from HbA1c. In this study we therefore analysed data from the Diabetes Control and Complications Trial (DCCT) to assess the relationship between MBG, HbA1c and glucose variability with regard to the risk of cardiovascular disease in patients with type 1 diabetes.
Methods: Pre- and postprandial seven-point glucose profiles were collected quarterly during the DCCT in 1441 individuals. The relationship between time to first cardiovascular event and MBG, HbA1c and daily SD of blood glucose was assessed by Cox regression after adjusting for the known risk factors of macrovascular disease and the treatment groups of the patients.
Results: Cox regression showed MBG to be predictive of a cardiovascular event (p=0.019), but not HbA1c (p=0.858). A rise of 1 mmol/l in MBG was associated with an 11% rise in cardiovascular risk. MBG remained highly predictive (p=0.015) even after adjustment for HbA1c values and glucose variability.
Conclusions/interpretation: This study has shown that during the DCCT MBG was a better predictor of the macrovascular complications of type 1 diabetes than HbA1c. It indicates that the cardiovascular risk associated with hyperglycaemia appeared within the time period of the study and that blood glucose rather than HbA1c may be the preferred means of assessing this risk.