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