HbA1c Levels Could Help Predict Heart Attack Risk Regardless of Sex

August 31, 2020

Analysis of the UK Biobank cohort details associations between increased HbA1c levels and risk of myocardial infarction in patients regardless of sex.

While the link between adverse cardiovascular events and diabetes is understood and well-established, new research suggests HbA1c levels could help predict patients at increased risk of myocardial infarction.

Results of the study, which was carried out by investigators from the George Institute for Global Health and Johns Hopkins University, suggest myocardial infarction rates were greater in men with diabetes compared to women and each 1% increase in HbA1c was linked to an 18% increase in risk of myocardial infarction regardless of sex.

“Although the incidence of MI was higher in men than women, the presence of diabetes is associated with a greater excess relative risk of MI in women. However, each 1% higher HbA1c was associated with an 18% greater risk of MI in both women and men,” wrote investigators in their conclusion.

In an effort to better understand the apparent risks of cardiovascular events associated with diabetes and glycemic control, investigators designed atrial to compare the prevalence of events among patients with type 2 diabetes. With this in mind, the investigators chose the UK Biobank to identify a cohort for inclusion in their study.

From the UK Biobank cohort, which contains more than 500k patients, investigators identified a group of 471,399 patients for inclusion. At baseline, 6% of men and 3.5% of women had a previous diagnosis of diabetes and these patients had a median hbA1c of 6.7%. During a follow-up period lasting a mean of 8.9 years, a total of 7316 myocardial infarction events occurred in the study cohort. Investigators noted this equated to an incidence of 9.3 per 10,000 person-years (95% CI, 8.9-9.7) for women and 27.6 per 10,000 person-years (95% CI, 26.8-28.3) for men.

Investigators noted analyses assessing HbA1c, diabetes, and myocardial infarction events were adjusted for factors including age, smoking, BMI, systolic blood pressure, use of antihypertensive medication, total cholesterol, use of lipid-lowering medication, and use of glucose-lowering therapies.

Following adjustment, results indicated women had lower incidence rates of myocardial infarction per 10,000 person-yearsthan men for the no diabetes (8.7 [95% CI, 8.2-9.2] vs 25.4 [95% CI, 24.5-26.3]), prediabetes (10.9 [95% CI, 9.8-12.0] vs 29.7 [95% CI, 27.5-31.9]), undiagnosed diabetes (14.3 [95% CI, 8.4-20.1] vs 38.9 [95% CI, 30.2-47.6]) and previously diagnosed diabetes (20.4 [95% CI, 17.1-23.6] vs 46.1 [41.4-50.8]) subgroups. Further analysis yielded similar results for individual without previously diagnosed diabetes and those with previously diagnosed diabetes at different HbA1c levels.

Additionally, investigators found previously diagnosed diabetes was associated with a greater risk of myocardial infarction in women (HR, 2.33; 95% CI, 1.96-2.78) than men (HR, 1.81; 95% CI, 1.63-2.02), with a women-to-men ratio of HRs of 1.29 (95% CI, 1.05-1.58). When assessing the impact of HbA1c, results suggest each 1% increase in HbA1c, independent of diabetes status, was associated with an 18% increase in risk of myocardial infarction—investigators noted this effect was greater in women (HR, 1.24; 95% CI, 1.20-1.28) than men (HR, 1.14; 95% CI, 1.10-1.19).

“The incidence of MI was considerably higher in men than women for diabetes status and across levels of HbA1c, the presence of previously diagnosed diabetes was associated with a greater excess relative risk of MI in women than in men. Each 1% higher HbA1c, independent of diabetes status, was associated with an 18% greater risk of MI in both women and men,” wrote investigators. “This study adds to the growing body of evidence on sex differences in the risk of MI, and other CVD phenotypes, associated with diabetes.”

This study, “Diabetes, Glycated Hemoglobin, and the Risk of Myocardial Infarction in Women and Men: A Prospective Cohort Study of the UK Biobank,” was published in Diabetes Care.