Test may help improve prediction of risk of cardiovascular disease in diabetics

Measuring hemoglobin A1c (HbA1c) levels in patients with diabetes is associated with improvement in models for predicting risk for cardiovascular disease (CVD), according to a report published Online First today by Archives of Internal Medicine, one of the JAMA/Archives journals.

According to background information in the article, diabetes has been recognised as a risk factor for CVD. But recent research indicates that the level of risk may vary among patients with diabetes. “Simulated cost-benefit analyses have suggested that this variability in CVD risk could provide an opportunity for tailored preventive therapy in diabetic patients,” write the authors. They sought to investigate the predictive value of HbA_1c levels; this test reflects the average blood glucose level over the previous two to three months, and generally indicates how well the diabetes is being managed.

Nina P. Paynter, Ph.D., from Brigham and Women’s Hospital, Boston, and colleagues, used data from participants of the Women’s Health Study and the Physician’s Health Study II. To generate the model, they included data from 24,674 women, of whom 685 had diabetes at baseline, and 11,280 men, of whom 563 had diabetes at baseline. Questionnaires provided participants’ health history, and baseline blood samples were evaluated for cholesterol, C-reactive protein and HbA_1c levels. The researchers followed up participants for incident (new cases) CVD; women were followed up for a median (midpoint) of 10.2 years and men for a median of 11.8 years.

During follow-up, 125 cardiovascular events occurred in the 685 women with diabetes and 170 events occurred in the 563 men with diabetes (compared with 666 and 1,382 events, respectively, in participants without diabetes). In both sexes, including HbA_1c into risk modeling for CVD improved prediction of CVD compared to classification of all diabetic participants as high risk (10-year risk at least 20 percent). This association was especially pronounced in women. The risk modeling demonstrated that 71.9 percent of female diabetic participants had less than a 20 percent risk of CVD over 10 years, whereas only 24.5 percent of male diabetic participants had a predicted 10-year CVD risk of less than 20 percent. In models that included a term for HbA_1c, there was substantial improvement in CVD risk prediction for women, and more modest improvement in risk prediction for men. Using a yes/no term for diabetes instead of HbA_1c also improved prediction over classification as high risk in both men and women. In women, however, HbA_1c further improved prediction over the yes/no term.

“We found that in these large population-based cohorts of both men and women, presence of diabetes alone did not confer a 10-year risk of CVD higher than 20 percent, and measurement of HbA1c level in diabetic subjects improved risk prediction compared with classification as cardiovascular risk equivalent,” note the researchers. They propose that the difference in risk between the sexes may be partly attributed to the increase in CVD risk with age and the delayed risk in women. The authors call for further research to replicate their results, but conclude, “Our findings suggest that the improvement in CVD risk prediction, and possibly calibration, obtained with adding HbA_1c levels is highest in lower-risk populations.”

(Source: JAMA/Archives: Archives of Internal Medicine)

More information

For more information on diabetes, including different types of diabetes, blood glucose and dietary control, and long-term complications, as well as some useful videos, see Diabetes.

For more information on keeping your heart healthy, including information on how the heart works, the effect of cholesterol and eating for heart health, as well as some useful videos and tools, see Heart Health.