Approximately one-third of women who were at low atherosclerotic cardiovascular disease (ASCVD) risk had coronary artery calcium (CAC), according to a meta-analysis of five population-based cohorts.

The researchers found that the presence of CAC was associated with an increased risk of ASCVD. Adding CAC to other risk factors led to a small increase in predicting ASCVD, as well.

Lead researcher Maryam Kavousi, MD, PhD, of the Erasmus University Medical Center in Rotterdam, the Netherlands, and colleagues published their results online Nov. 15 in JAMA.

The findings were also presented in an oral abstract session at the American Heart Association Scientific Sessions in New Orleans.

Previous research showed that scanning for CAC helps detect subclinical coronary atherosclerosis, according to the researchers. They added that the presence of CAC in asymptomatic people is associated with a higher risk for coronary heart disease and all-cause mortality.

This meta-analysis included 6,739 women who had a 10-year ASCVD risk lower than 7.5 percent. The women enrolled in the Dallas Heart Study, the Framingham Heart Study, the Heinz Nixdorf Recall study, the Multi-Ethnic Study of Atherosclerosis and the Rotterdam Study. They were excluded if they had a history of coronary artery disease, stroke or chronic kidney disease, had a low-density lipoprotein cholesterol level of 190 mg/dL or higher or were older than 79 years old.

The researchers calculated the 10-year risk for ASCVD using variables from the American College of Cardiology/American Heart Association pooled cohort equations. The variables were age, total and high-density lipoprotein cholesterol, current smoking status, systolic blood pressure, use of antihypertensive medications and diabetes.

The women with CAC were older, had a more unfavorable cardiovascular risk profile and had higher prevalences of diabetes and a family history of premature coronary heart disease compared with those without CAC.

During a median follow-up period of 7 to 11.6 years, there were 165 ASCVD events, including 64 nonfatal MIs, 29 coronary heart disease deaths and 72 strokes.

The incidence rates for an ASCVD event ranged from 0.45 per 1,000 person-years to 3.15 per 1,000 person-years in the group without CAC and from 3.08 per 1,000 person-years to 7.50 per 1,000 person-years in the group with CAC.

The presence of CAC was associated with an ASCVD incidence rate of 4.33 per 1,000 person-years, and the absence of CAC was associated with an ASCVD incidence rate of 1.41 per 1,000 person-years.

When the researchers added CAC to traditional risk factors, they found that the C statistic increased from 0.73 to 0.77 and that there was a continuous net reclassification improvement of 0.20 for ASCVD prediction.

They also noted a few limitations of the meta-analysis, including that they chose five cohorts that had CAC data available. They also mentioned that most of the women were of European descent, so the results might not be generalizable to other groups. In addition, there were a small number of ASCVD events for several of the CAC categories.

“Findings from the current study support the need for further studies to better define which group of low-risk women have the highest yield from CAC testing,” the researchers wrote. “Besides considering the cost-effectiveness, the ultimate decision regarding the application of CAC testing among women at low cardiovascular risk remains to be verified in randomized clinical trials testing the value of CAC in improving the outcomes.”