Dr. Nilay Shah analyzes the coronary artery calcium scan of a patient in his clinic at Northwestern Medicine in Chicago. Credit: Ben Schamisso / Northwestern University
Who Actually Benefits From a Heart Calcium Scan? A Decade-Long Study Has an Answer
In A Nutshell
- A decade-long study of 6,098 adults found that adding a coronary artery calcium (CAC) scan to standard heart risk calculators only modestly improved predictions overall.
- The scan’s biggest payoff showed up in people with borderline heart risk, where those with high calcium scores had roughly seven times the 10-year event rate of those with a score of zero.
- Nearly half of participants had detectable calcium buildup at the study’s start, and those with calcium tended to be older with more risk factors like high blood pressure and diabetes.
- Updated 2026 cardiology guidelines already recommend the scan mainly for patients whose risk falls in an uncertain middle zone, and this research backs that narrower approach.
Many Americans in their 50s and 60s sit in a doctor’s office facing the same question: does a borderline heart-risk score mean it’s time to start a daily statin? For years, cardiologists have offered a tiebreaker, a CT scan that measures calcium buildup in the heart’s arteries. It sounds like the kind of test that should settle things once and for all. New research suggests that for a lot of people, it barely moves the needle.
A study published in JAMA followed more than 6,000 adults for a decade and found that adding a coronary artery calcium, or CAC, score to the newest cardiovascular risk calculator only modestly sharpened the predictions overall. Doctors will still order the calcium scan, and for some patients it will meaningfully change the treatment plan. But the gains were uneven, concentrated almost entirely in one group.
The findings matter because CAC scoring is increasingly used to help refine estimates of heart risk. This research, led by scientists at Northwestern University’s Feinberg School of Medicine, offers a more precise answer about who that calcium scan actually helps: mainly those stuck in a gray zone of risk, not everyone who walks through the door.
Study Tracked Calcium Scans for 6,098 Adults Over Ten Years
The research team pulled data from the Multi-Ethnic Study of Atherosclerosis, a long-running project that recruited adults between the ages of 45 and 79 from six cities across the country, including Chicago, Baltimore, and Los Angeles. None of the 6,098 participants included in this analysis had cardiovascular disease when the study began between 2000 and 2002. Just over half were female, and the group included Black, Chinese, Hispanic, and white participants.
Every participant received a CT scan at the start of the study to measure coronary artery calcium, a number reflecting how much hardened plaque has built up in the heart’s arteries. A score of zero means no detectable calcium; scores climb into the hundreds as plaque accumulates. Researchers also calculated each person’s 10-year heart disease risk using PREVENT, a newer risk equation the American Heart Association introduced to replace an older tool that tended to overestimate danger. About half the participants had some detectable calcium at the start of the study, and those with calcium tended to be older and carry more risk factors like high blood pressure and diabetes.
Participants were tracked for a decade through regular checkups and phone calls, and researchers recorded every heart attack and stroke that occurred. In total, 366 participants, about 6%, experienced one of these events. Researchers then tested how much better their predictions got once the calcium score was folded into the PREVENT equation.
Borderline-Risk Patients Saw a Sevenfold Gap in Outcomes
Adding the calcium score barely moved the needle on the model’s overall accuracy. It also reshuffled some patients into new risk categories, mostly in the right direction, correctly flagging people as lower-risk more often than it wrongly did so. But for a small slice of people who went on to have a heart attack or stroke, the scan gave false reassurance, nudging them into a lower-risk bracket.
The clearest benefit showed up in one specific slice of the group: people who landed in the “borderline” risk category, meaning their 10-year odds of a heart attack or stroke fell between 3% and 5%. Among these 1,115 participants, the calcium score separated people into groups with sharply different levels of risk. Those with a calcium score of zero had an event rate of just 1.9% over the following decade. Those with scores of 300+, a sign of heavy plaque, saw their event rate climb to 14.3%, roughly seven times higher. That’s a meaningful gap for a doctor and patient trying to decide whether starting a statin makes sense.
The study’s authors summarized their findings plainly: “Reclassification results support selective use of CAC in those with borderline to intermediate risk estimated by the PREVENT-ASCVD equations.” In other words, the calcium scan earns its keep for a specific slice of patients, not the general population.
New Guidelines Already Point to Selective Scanning
Cardiology guidelines updated in 2026 already lean this direction, recommending that calcium scoring be considered for selected patients whose calculated risk falls between 3% and 10% when the treatment decision is still uncertain. This study backs up that narrower approach with long-term outcomes from a large community-based group.
None of this means the calcium scan is worthless. For someone hovering in that borderline zone, a score of zero might offer genuine reassurance to skip a statin, while a high score could nudge a hesitant patient toward treatment. The smarter question isn’t whether to get one. It’s whether the risk numbers already in hand put someone in the narrow window where the scan actually changes the answer.
Disclaimer: This article is intended for general informational purposes and does not constitute medical advice. Anyone with questions about heart disease risk or statin therapy should consult a qualified healthcare provider.
Paper Notes
Limitations
The study drew its calcium scores and risk data from a group already used to help build the PREVENT risk equations, which may make the equations look more accurate in this sample than they would in a fresh, unrelated population. The findings apply to adults between 45 and 79; whether calcium scoring performs differently in younger adults, who tend to have far less arterial plaque to begin with, was not tested. Calcium scores in the study were collected specifically for research purposes rather than through routine clinical scans, so results in everyday medical practice could differ somewhat.
Funding and Disclosures
The research was funded by the National Heart, Lung, and Blood Institute and the American Heart Association. Several authors disclosed financial ties to pharmaceutical and medical device companies, including Amgen, Novartis, Eli Lilly, and Heartflow, for work outside this study. The funding organizations had no role in designing the study, analyzing the results, or deciding to publish the findings.
Publication Details
The study, “Predictive Utility of Coronary Artery Calcium Score Added to the PREVENT Atherosclerotic Cardiovascular Disease Equations,” was authored by Xiaoning Huang and colleagues from Northwestern University Feinberg School of Medicine and several partnering institutions. It was published online in JAMA on August 26, 2026. DOI: 10.1001/jama.2026.13233.
