Regardless of a patient’s age or level of coronary artery calcification (CAC), each incremental improvement in cardiorespiratory fitness (CRF) contributes to a lower risk of adverse cardiovascular events, researchers reported in Circulation.
“Based on our findings, the clinical recommendation to improve or maintain fitness to reduce CVD (cardiovascular disease) risk associated with CAC may be broadly applicable across the spectrum of ages and CAC burden,” wrote lead author Nina B. Radford, MD, with the Cooper Clinic in Dallas, and colleagues. “Our results suggest that CRF may be especially important when assessing CVD risk in those with higher CAC levels.”
CAC is a significant predictor of CVD events such as strokes and heart attacks, while CRF has been shown to attenuate the risk of those events. However, Radford et al. pointed out few studies have investigated the relationship between CAC and CRF at varying levels of calcification.
They studied 8,245 men without clinical CVD who underwent preventive examinations that included measurements of CAC and CRF between 1998 and 2007. A treadmill test assessed participants’ metabolic equivalents (METs), a measurement of exercise intensity based on oxygen consumption.
Over an average follow-up of 8.4 years, there were 383 CVD events, which included cardiovascular death, non-fatal myocardial infarction, atherosclerotic stroke, coronary artery bypass surgery and percutaneous coronary intervention.
Compared to a CAC score of 0, those with CAC 1-99 were at 1.85 times the risk of experiencing a CVD event, while scores of 100-399 and 400-plus were linked to triple and six times the risk, respectively. After adjusting for CAC level, each MET increase was associated with an 11 percent lower risk of CVD events in a prediction model.
“In each of the follow-up periods, higher CRF attenuates the increase in annual total CVD incidence rates associated with higher CAC levels,” the researchers wrote. “For example, in the lowest fit (5 MET) participants in the 25-year follow-up group, there is almost a five-fold increase in annual total CVD incidence rates in participants with CAC ≥400 compared to those with CAC 0. In contrast, among the highest fit (15 METs) participants in this same group, there is only a two-fold increase in annual total CVD incidence rates in participants with CAC ≥400 compared to those with CAC 0.”
This finding, the authors said, supports the American Heart Association’s suggestion that fitness level be used as a clinical vital sign. In addition, Radford et al. wrote improving fitness level could be a widely available, cost-effective means to reducing CVD events—although lifestyle modifications rely on patient adherence.
One limitation of the study is it only included men, most of whom were white, well-educated and of middle to upper socioeconomic status. More work is needed to assess the relationship between CAC, CRF and CVD events in women and other ethnic and racial groups, the researchers wrote.