The effect of adjustable risk factors on the CAC score
Several factors have been shown to increase CAC, including obesity and smoking. Young adults with a higher waist girth (men ≥84.3 cm; women ≥75.5 cm) have twice the risk of developing CAC the HNR study has shown that current smoking was positively associated with CAC. Interestingly lifetime of not smoking would show benefits in reducing the risk of developing CAC. However, it is known that lifestyle factors alter early atherosclerotic vascular disease risk; therefore, it cannot be determined whether CAC regression through lifestyle modification is an independent risk factor for lowering the risk of CAD and CVA.43
Due to the importance of CAC in the prediction of adverse cardiovascular events, much research has been done to identify how various lifestyle factors may affect it. Amongst those factors is obesity, as young adults with a higher waist girth are more likely to have CAC.44 In addition, other well-described risk factors of stroke, such as smoking, have been shown to increase the risk of developing CAC.45 In addition, exercise has been reported to be associated with CAC, with higher CAC scores being more common in sedentary groups.46 Interestingly, the same study showed that the detrimental effects of a lack of exercise were accentuated in those with a higher CAC score, as all-cause mortality was low in those with a CAC of zero regardless of exercise, but significantly increased in those who had higher CAC scores and did not perform an exercise.
These results indicate that not only can CAC scoring be used as a reflection of the effect of various well-known risk factors of cerebrovascular disease, but that the CAC score in and of itself may act to modify the effect of lifestyle interventions on mortality; therefore, CAC scores may help physicians identify patient groups most likely to benefit from certain lifestyle modifications.
As previously mentioned, the impact of statins on CAC is not consistent amongst studies; however, CAC scores can be used to inform the initiation of statin therapy, particularly in intermediate-risk patients. Since statins are well known to reduce the risk of stroke,47 CAC can be said to play an important in the primary prevention of CVA. In addition, aspirin therapy, which has a limited role in the primary prevention of CVD, may be guided through the use of CAC. Analysis of the MESA study showed that participants had a CAC score of greater than 100 were much more likely to benefit from aspirin therapy than those with a CAC score of 0, as aspirin resulted in a greater decrease of cardiovascular events (including stroke) in the higher CAC group. Given the concerning risk of bleeding that may arise due to aspirin use, better guidance of aspirin therapy using CAC scoring may allow optimal patient selection and thus lead to improved outcomes.48