When Zero Isn’t Zero: What You Need to Know About Coronary Calcium Scores and Women’s Heart Health

For years, coronary artery calcium (CAC) scoring has been one of the best tools we have for preventing heart attacks and strokes. It gives doctors a way to see the buildup of atherosclerosis—plaque in your arteries—long before symptoms appear.

Using a simple, non-invasive CT scan, CAC produces a number that directly reflects your risk for future cardiovascular events. The higher your CAC score, the higher your risk. That clarity has changed how we approach prevention.

But there’s one big catch: CAC can only measure what it can see—calcium. And for many people, especially women, that means part of the story is being left out.

CAC Scores 101:

Long before calcium shows up on a scan, plaque has already started to build inside artery walls. Here’s how it happens:

1. Lipid particles (apoB-containing) sneak into the vessel wall and become oxidized.
2. The immune system reacts, sending in white blood cells to “clean up” the mess.
3. These cells turn into foam cells, forming soft, fatty streaks.
4. Over time, inflammation and scarring lead to fibrous and, eventually, calcified plaques.

When enough calcium accumulates, CAC scoring can finally detect it. The CT scan identifies each calcified area, scoring them by size and density to create an overall Agatston score (named for the cardiologist who developed it).

Scores fall into general categories:

• 0: No visible calcium (low short-term risk)
• 1–99: Mild plaque buildup
• 100–399: Moderate plaque burden
• 400+: Extensive atherosclerosis, high risk
  
  

In general, the higher the number, the greater the need for aggressive prevention—such as with statins or other lipid-lowering treatments.

The Blind Spot: What CAC Can’t See:

Here’s the paradox: it’s not the calcified plaque that’s most dangerous. It’s the soft, non-calcified plaque that’s more likely to rupture and cause a heart attack or stroke.

Calcification actually represents the body’s healing response—an attempt to stabilize the lesion. Statins, for example, help by promoting plaque calcification, making vulnerable plaques safer.

So, while CAC is excellent at showing the total burden of stable plaque, it misses the soft, high-risk lesions that can do the most damage. That means CAC gives us only the tip of the iceberg when it comes to cardiovascular risk.

And this limitation matters even more for women.

 

Why CAC Can Underestimate Risk in Women:

In the years before and around menopause, women tend to have more soft, non-calcified plaque and less calcified plaque. On average, women start developing visible calcium deposits about 10 years later than men.

Studies back this up:

• In the MESA study, 62% of women had a CAC score of 0, compared with 40% of men.
• Imaging research shows that women are more likely to experience plaque erosion, while men more often have plaque rupture—both dangerous, but only one (rupture) is detected by CAC.
• High-risk plaque features predict events far more strongly in women (odds ratio 34.5 vs. 4.1 in men).

That means a woman in her 40s or 50s might have significant non-calcified plaque—and still score a zero on her CAC scan.

What This Looks Like in Real Life:

Imagine a 52-year-old man with a CAC score of 72 and his 50-year-old wife with soft, non-calcified plaques. Based on CAC alone, the man’s score would trigger aggressive treatment. The woman’s score of zero might be falsely reassuring—even though her actual risk may be higher.

By the time her calcium “catches up” a decade later, valuable prevention time has been lost.

What to Do About It:

CAC remains a powerful tool for risk assessment—but it’s not the whole story, especially for women.

Here’s what that means clinically:

• A high CAC score is concerning in both sexes and should prompt treatment.
• A score of zero can only be reassuring if all other risk factors—apoB, blood pressure, glucose, lifestyle—are healthy.
• If other major risk factors are present, they should still be treated aggressively, regardless of what the CAC says.
  
  

For women, particularly those with symptoms or multiple risk factors but a zero CAC score, additional imaging can provide answers.

Beyond CAC: Seeing the Whole Picture with Cleerly

When risk remains uncertain, Coronary CT Angiography (CCTA) and advanced imaging technologies like the Cleerly test can reveal the non-calcified plaque that CAC misses.

The Cleerly test uses cutting-edge AI to analyze every millimeter of coronary arteries, mapping not only calcium but also soft, fibrous, and mixed plaques. It paints a complete picture of cardiovascular risk—one that’s especially important for women.

Coming Up Next:

“Beyond Calcium: How the Cleerly Test Sees What CAC Can’t.”

In our next blog, we’ll explore how Cleerly’s AI-driven imaging technology gives clinicians and patients a full view of heart disease risk—years before a heart attack ever happens.

 

References

1. Shaw LJ, Min JK, Nasir K, et al. Sex differences in calcified plaque and long-term cardiovascular mortality: observations from the CAC Consortium. Eur Heart J. 2018;39(41):3727-3735. doi:10.1093/eurheartj/ehy534
2. McClelland RL, Chung H, Detrano R, Post W, Kronmal RA. Distribution of coronary artery calcium by race, gender, and age: results from the Multi-Ethnic Study of Atherosclerosis (MESA). Circulation. 2006;113(1):30-37. doi:10.1161/CIRCULATIONAHA.105.580696
3. Bigeh A, Shekar C, Gulati M. Sex differences in coronary artery calcium and long-term CV mortality. Curr Cardiol Rep. 2020;22(4):21. doi:10.1007/s11886-020-1267-9
4. Plank F, Beyer C, Friedrich G, Wildauer M, Feuchtner G. Sex differences in coronary artery plaque composition detected by coronary computed tomography: quantitative and qualitative analysis. Neth Heart J. 2019;27(5):272-280. doi:10.1007/s12471-019-1234-5
5. Attia, P. (2023). Outlive: The Science and Art of Longevity. New York: Harmony Books.
6. Attia, P. (Host). The Drive [Podcast]. Episode: “Heart Disease: Understanding Risk and Early Detection.” Accessed 2024. https://peterattiamd.com/podcast/