Understanding the Coronary Artery Calcium (CAC) Score
A coronary artery calcium (CAC) score, also known as a heart scan, is a non-invasive test that uses a CT scan to measure the amount of calcified plaque in the arteries supplying the heart. Plaque is a buildup of fat, cholesterol, and calcium that can lead to the narrowing of arteries, a condition called atherosclerosis. A higher CAC score indicates a greater amount of calcified plaque and a higher risk of heart disease and related events like heart attacks or strokes.
Unlike cholesterol tests, which measure current levels, the CAC score reflects a history of plaque buildup over time. For a 75-year-old, the score must be interpreted differently than for a younger person because calcium accumulation is a natural part of the aging process. For this reason, a high score in a 75-year-old does not necessarily carry the same alarm as it would for a 50-year-old.
The Context of Age and Average Scores
For a 75-year-old, the idea of an "average" score can be deceiving. As people age, plaque naturally accumulates, and a coronary calcium scan will likely detect some level of calcification. Research shows that most individuals aged 75 and older have a CAC score greater than 100. This highlights why interpreting the score relative to one's age and other risk factors is critical. For example, a score of 100-300, which indicates moderate plaque, might place a younger person in a higher-risk category, but is common for a 75-year-old.
This is where percentile rankings become more useful. Percentiles compare a patient's score to others of the same age and sex. A study published in Circulation: Cardiovascular Imaging established specific CAC percentiles for individuals aged 75 and older. For this age group, a score greater than 100 often falls below the 75th percentile, which is a traditional threshold for high risk in younger individuals.
Interpreting Score Ranges for a 75-Year-Old
- Score of 0: This is an excellent result for any age, and for a 75-year-old, it is a very strong indicator of low risk. Studies show that a CAC score of zero in older adults corresponds to a very low risk of obstructive coronary artery disease. Approximately 10-20% of people aged 75 or older have a score of zero.
- Score 1-99 (Mild Plaque): While this indicates some plaque, it suggests a relatively low risk of significant coronary disease for a 75-year-old. It is a sign to focus on healthy lifestyle choices and monitor risk factors.
- Score 100-399 (Moderate Plaque): For a 75-year-old, this score is common but indicates a moderate to high likelihood of coronary artery disease. It is often a signal for more aggressive management of risk factors, possibly including statin medication.
- Score >400 (Extensive Plaque): This indicates a significant burden of calcified plaque and a high risk of heart attack. Even in a 75-year-old, this score is a major red flag, potentially requiring further testing and significant interventions.
The Importance of a Zero Score in Later Life
Achieving a CAC score of zero at age 75 or older is a highly positive indicator for heart health. It suggests that despite the aging process, the individual's arteries have remained free of calcified plaque. This result provides strong evidence against the presence of significant obstructive coronary artery disease. A zero score can often lead to a less aggressive treatment approach, reducing the need for medications like statins, especially if other risk factors are low. It is a powerful piece of information that can help guide personalized care for senior adults.
Factors Influencing Your Score and Next Steps
Your CAC score is not the only factor in determining your risk. A physician will consider your results alongside other conventional risk factors.
- Other Risk Factors: These include high cholesterol, high blood pressure, diabetes, smoking history, family history of heart disease, obesity, and a sedentary lifestyle. Your medical team will assess the complete picture.
- Lifestyle Changes: For any non-zero score, lifestyle modifications are crucial. This includes adopting a heart-healthy diet (low in saturated fat, sodium, and sugar), engaging in regular physical activity, managing stress, and quitting smoking.
- Medication: Depending on your overall risk profile and the score, a doctor may recommend medication, such as statins, to manage cholesterol and mitigate risk.
- Further Testing: For very high scores, additional tests like a coronary CT angiography may be needed to get a more detailed view of the coronary arteries.
Coronary Calcium Score vs. Risk Percentile Table
| CAC Score (Agatston Units) | General Interpretation | Meaning for 75-Year-Old (Relative Risk) |
|---|---|---|
| 0 | No plaque detected | Very low risk of obstructive CAD |
| 1–99 | Mild plaque burden | Low risk relative to peers, but plaque is present |
| 100–399 | Moderate plaque burden | Common in this age group, but requires aggressive risk management |
| ≥400 | Extensive plaque burden | High risk of future cardiac events, requires immediate attention |
Conclusion: Interpreting the Score in Context
For a 75-year-old, there is no single "average" calcium score to aim for. Due to the natural progression of atherosclerosis, scores tend to be higher than in younger age groups. Therefore, the interpretation of the score is nuanced and must be done in the context of age, sex, and individual health factors. A score should not be viewed in isolation but as one important piece of information to help guide preventive treatment and lifestyle decisions. A CAC score of zero is a powerful indicator of low risk, while any non-zero score should serve as a motivator for proactive heart health management, working closely with a healthcare provider.
Learn more about heart health at the American Heart Association website: https://www.heart.org/en/healthy-living/healthy-lifestyle/how-to-help-prevent-heart-disease-at-any-age.
