CardioExchange Archive

Although blood glucose and glycated hemoglobin (HbA1c) play a central role in diabetes, the value of these measurements to assess cardiovascular risk has been unclear. Now, in a paper published in JAMA, members of the Emerging Risk Factors Collaboration analyze data from nearly 300,000 people without known diabetes or cardiovascular disease who were enrolled in 73 prospective studies.

The authors found that adding glycemia measures to conventional cardiovascular risk assessment provided little additional prognostic information. Further, adding information about blood glucose did not result in a significant improvement in the classification of people used to help decide about preventive treatment.

One somewhat surprising finding was that four different measures of glycemia independently resulted in a  J-shaped curve of cardiovascular risk — although lower glycemia levels were generally associated with lower levels of risk, at the extreme lowest level there was a rebound in risk. This finding “should encourage further studies to test whether very low glycemia levels are markers of ill health,” write the authors.

Another nonintuitive finding was that HbA1c measures were “at least equal” to fasting, random, and postload plasma glucose levels in assessing risk. “This finding challenges suggestions that postload glucose levels predict CVD incidence more strongly than do other glycemia measures,” they say.

The authors conclude: “Contrary to recommendations in some guidelines, the current analysis of individual-participant data in almost 300,000 people without known diabetes and CVD at baseline indicates that measurement of HbA1c is not associated with clinically meaningful improvement in assessment of CVD risk.”