CAC Score of Zero at Age 73: Prevalence and Clinical Significance
A CAC score of zero at age 73 is uncommon but not rare, occurring in approximately 10-20% of individuals in this age group, and represents an exceptionally favorable cardiovascular prognosis regardless of other risk factors. 1
Prevalence in Older Adults
While a zero CAC score becomes progressively less common with advancing age, it is still observed in a meaningful proportion of older individuals:
In large asymptomatic cohorts, approximately 41% of all patients across age groups had CAC = 0, though this percentage decreases substantially with age. 1 In the specific context of a 73-year-old, the prevalence would be considerably lower than this overall average, as age is the strongest predictor of CAC presence. 1
The MESA model demonstrates that a CAC score of 100 corresponds to an arterial age of approximately 73 years, suggesting that zero calcium at this chronological age represents a vascular age significantly younger than expected. 1 This indicates your patient has exceptional vascular health for their age.
Clinical Significance and Prognosis
The "power of zero" applies robustly even in older individuals:
Annual mortality remains <1% for over 15 years in patients with CAC = 0, and this favorable prognosis holds true even for those classified as high risk by traditional risk scores. 1 This means your 73-year-old patient has a cardiovascular risk profile similar to a much younger individual.
The event rate for an 80-year-old with CAC = 0 and no other risk factors approximates that of an average 50-year-old with no risk factors, demonstrating the powerful risk-downgrading effect of zero calcium. 1 Your 73-year-old patient essentially has the cardiovascular risk of someone decades younger.
In systematic reviews, only 0.47% of asymptomatic patients with CAC = 0 experienced adverse cardiovascular events during 50-month follow-up. 1
Important Caveats
The presence of risk factors can truncate the durability of the zero CAC "warranty period," particularly in diabetic patients after 5 years. 1
While no difference in 5-year mortality exists between diabetic and nondiabetic CAC = 0 patients, diabetic patients show a nonlinear increase in mortality after 5 years. 1
Family history of premature CHD increases risk by approximately 70% even with CAC = 0, though absolute event rates remain low. 2
Clinical Management Recommendations
For your 73-year-old patient with CAC = 0:
Reassurance is appropriate, as this represents exceptionally low cardiovascular risk. 3 The patient should be informed they have vascular health far superior to age-matched peers.
Statin therapy is generally not recommended based solely on CAC = 0, even in older individuals, unless other high-risk features are present. 4 Focus should remain on lifestyle optimization.
If the patient has diabetes or multiple cardiovascular risk factors, consider repeat CAC scanning in 5 years, but not sooner. 5, 4
Continue standard preventive measures including blood pressure control, lifestyle modification, and management of any existing risk factors. 6
The finding of zero calcium at age 73 should be viewed as highly favorable and unusual, representing a patient who has successfully avoided significant atherosclerotic burden despite advancing age.