A1c predicts cardiovascular disease, death in nondiabetics

Compared to fasting glucose tests, A1c levels are similarly predictive of diabetes development and better predict cardiovascular disease and death, a new study of nondiabetic adults found.

The study used blood samples from more than 11,000 black or white adults participating in the Atherosclerosis Risk in Communities study. Using a baseline reference risk of 5.0% to 5.5%, the study found that study participants with an A1c of 5.5% to less than 6% had an 86% increased risk of being diagnosed with diabetes, while patients with A1cs between 6% and 6.5% and over 6.5% had 4 and 16 times the risk, respectively. The same trends were true for coronary heart disease and stroke. Study participants with A1cs under 5% had a reduced risk for all three outcomes. The associations remained significant after adjustment for baseline fasting glucose level, whereas the association between fasting glucose and cardiovascular disease and death was not significant after adjustment.

The association between A1c and death from any cause was found to have a J-shaped curve (with a low point between 5% and 5.5%), which suggests that there should be further research on the health risks of a low-normal glycemic state, the study authors concluded. The study also looked at racial differences in A1c. Although blacks had higher baseline A1cs and were less likely to be diagnosed with diabetes, the association between A1c and cardiovascular disease followed the same pattern for both studied races. The study was published in the March 4 New England Journal of Medicine.

The results indicated that even patients with A1cs in the normal range may be at an increased risk for coronary heart disease, stroke and death, the authors concluded. This finding is complicated by the fact that other trials have found little benefit, and sometimes harm, in lowering A1cs to prevent cardiovascular outcomes, the authors noted. Still, the study provides support for the recent recommendation to use A1c as a diagnostic test for diabetes, they concluded.