Here is our review of The Cooper Clinic’s Study on CAC scores in active people. It’s a good study with caveats as described below.
Staying Active and Alive, Despite an Increased CAC Score
Recent studies have demonstrated that life-long endurance athletes and extremely active individuals have more coronary artery calcification (CAC), a marker of coronary artery disease (CAD) risk, than less active individuals. But what should clinicians do once increased CAC is detected in active individuals, such as life-long endurance athletes? Exercise is associated with markedly reduced CAD events, so must clinicians forbid these patients from continuing to exercise?
DeFina and colleagues examined the incidence of all cause and cardiac mortality in participants in The Cooper Clinic Longitudinal Study. The study included 21,758 men. Women were not included because there were too few deaths in women. The men had baseline examinations between 1998 and 2013, and were followed until December 2014. Subjects were divided into three activity levels based on their self-reported physical activity and into two CAC groups: those with CAC vales > or < than 100 Agatston units (AU). The physical activity classification was performed at baseline based on the previous 3 months of exercise.
Those in the highest exercise group were more likely to have CAC scores >100, supporting the observation that large amounts of physical activity accelerate coronary calcification. The mean CAC level in the highest exercise group, those reporting >2999 metabolic equivalents of task or MET-minutes per week, was 807 AU, a very high value, but not different from the low (736 AU) and middle (680 AU) exercise groups. The men in the highest exercise group did not have a total or CAD mortality rate greater than those performing lesser amounts of activity.
This study has several important strengths. It addresses an important issue — whether the increased CAC in very active individuals increases mortality. It also includes a large number of subjects and has a mean follow-up of 10.4 years. But there are also limitations. Physical activity is based on self-report at baseline, so in addition to the possibility that subjects had inaccurately reported their activity, there is also the possibility that subjects curtailed their activity after learning that their CAC scores were high. Subjects could also have undergone treatments that alter their disease course based on their CAC values.
Also, despite there being more individuals in the high exercise group with CAC values >100 AU, the average CAC score was not different among the groups, leading one to expect no differences in outcomes. The similar average CAC scores among the different exercise groups also raises the possibility that the exercise was not responsible for the higher percentage of individuals with CAC values >100 AU in the most active group. Finally, non-fatal CAD events were not quantified, and one myocardial infarction can ruin your whole week, especially when it’s yours.
Nevertheless, the key result, that very active individuals with increased CAC do not have increased total and CAD mortality is an important message. More studies will be required to determine whether there is an increased risk of non-fatal CAD events and whether these patients can safely continue to exercise vigorously.
So, how should these very active patients with high CAC scores be managed? Present guidelines are based on expert opinion and suggest that such patients can continue to exercise without restriction if they have no evidence of exercise-induced ischemia or electrical instability and a resting left ventricular ejection fraction >50%.1 Their CAD risk factors should be treated aggressively. This approach is reasonable, but additional data are needed to be certain that this reasonable approach is the absolute best approach.
References
- Thompson PD, Myerburg RJ, Levine BD, Udelson JE, Kovacs RJ. Eligibility and disqualification recommendations for competitive athletes with cardiovascular abnormalities: Task Force 8: coronary artery disease: a scientific statement from the American Heart Association and American College of Cardiology. Circulation. 2015;132(22):e310-e314. https://www.ahajournals.org/doi/full/10.1161/CIR.0000000000000244
