EASD: CV Events Linked to Poor Glycemic Control

Poor glycemic control in diabetics is linked to an increased risk of cardiovascular events, a large retrospective study suggests.

Examining data from almost 70 000 diabetics enrolled in the Integrated Health Care Information System database (IHCIS), researchers from Yale report that rates of first acute MI and CABG, but not stroke, over more than two years of follow-up were higher for subjects with higher HbA1C levels at baseline.

Dr Joseph Thomas (Yale University, New Haven, CT) reported the results of the analysis at the European Association for the Study of Diabetes 2007 Meeting. While poor glycemic control has well-established ties to microvascular and macrovascular disease, the link with hard cardiovascular events is less clear, with much of the current debate on the cardiovascular safety of diabetes drugs–thiazolidinediones in particular–circling around the fact they were approved on the grounds that they successfully improved glucose control and not because of their effects on cardiovascular outcomes.
Now, with the caveat that the study was retrospective and included relatively healthy, younger individuals, Thomas said that it nevertheless provides insights into the importance of controlling glucose.

“An elevated index A1C is a significant risk factor for AMI and CABG, with poorer survival,” he said. “Glycemic control is associated with real-world, long-term macrovascular outcomes, and early intervention with intensive diabetes treatment may reduce macrovascular events.”

Thomas and colleagues stratified patients across quartiles of index HbA1C level, using the cut points of <6%, 6% to 7%, 7% to 9%, and >9%. Over a mean of more than two years of follow-up, unadjusted incidence rates were highest in the 7%-9% HbA1C group, seeming to level off above 7%. Of note, subjects in the highest HbA1C group also had the most other risk factors for CVD and were more likely to be taking cardiovascular medications and insulin.
Rates of AMI, CABG, and stroke per 1000 person-years

HbA1C level (%)	<6	6–7	7–9	>9
MI/CABG/stroke	76.5	80.5	81.7	65.2
AMI	16.5	18.2	21.6	20.6
CABG	4.4	6.0	6.9	6.9
Stroke	63.3	65.0	63.8	60.0

After adjustment for comorbidities and diabetes, lipid-lowering, and antihypertensive drugs, the link between high HbA1C levels and cardiovascular risk was even stronger. Compared with the <6% group, the hazard risk for the combined end point of AMI, CABG, and stroke was 8% higher in the 7%-9% HbA1C group and 15% higher in the >9% HbA1C group.
Kaplan-Meier survival curves looking at time to death/AMI pointed to significantly worse survival for subjects in the 7%-9% HbA1C group, with a hazard ratio of 1.33, and for subjects in the highest HbA1C category, with a hazard ratio of 1.57, as compared with subjects in the lowest HbA1C group. Similarly, for the end point of death/CABG, hazard ratios were also increased in these groups, at 1.38 and 1.56, respectively.
Reported at the European Association for the Study of Diabetes 2007 Meeting.