Calcium score: what this number reveals about your arteries by age

A calcium score measures, in a few minutes of CT scanning with no injection, the amount of calcium deposited in the arteries of the heart. It is mainly relevant for adults aged 40 to 75 with no symptoms whose cardiovascular risk remains uncertain. Its value: it shows the actual state of the coronary arteries, where cholesterol and blood pressure only give a probability. The same number does not read the same way at 45 and at 75.

Calcium score: definition and how it is calculated

The coronary calcium score is a number, from 0 to several thousand, that summarizes the calcium burden visible in the four main arteries of the heart. It is obtained with a chest CT scan synchronized to the electrocardiogram, without contrast dye. Image acquisition takes less than a minute and the whole exam about ten minutes.

The reference method dates from 1990. Arthur Agatston and his team scanned 584 people and defined a simple calculation: for each calcified lesion, the area is multiplied by a density coefficient, then all lesions are added up (Agatston et al., 1990). Since then, results have been expressed in “Agatston units”. The report usually gives the total, the breakdown by artery and sometimes a percentile based on age and sex.

Coronary calcium is not an isolated deposit: it marks long-standing atherosclerotic plaques. A high score does not mean that an artery is blocked, but that atherosclerosis is established and widespread. This information, the amount of disease already present, is what this scan provides and what blood tests cannot.

How calcium builds up in the arteries

Coronary calcium appears at a late stage of an atherosclerotic plaque, after years of LDL cholesterol infiltration and inflammation in the artery wall. The US National Heart, Lung, and Blood Institute describes atherosclerosis as a buildup of fatty plaque in the artery wall, a process in which inflammation plays a central part (NHLBI page on atherosclerosis). Calcification is partly an attempt by the body to heal this plaque.

Several steps lead from cholesterol to calcium visible on a scan:

• LDL particles enter the artery wall and become oxidized there;
• macrophages absorb them, turn into foam cells and release inflammatory signals;
• smooth muscle cells in the wall change behavior and start producing a bone-like matrix;
• tiny calcium particles (microcalcifications) form, then merge into dense plaques visible on the scan.

This process ties arterial calcification to aging. Chronic low-grade inflammation, senescence of vascular cells and cumulative exposure to risk factors add up over the years. The CAC score therefore reflects both your age and the history of your arteries: smoking, blood pressure, cholesterol, blood sugar.

One point often surprises people: the most calcium-dense plaques are not necessarily the most dangerous. Small, spotty calcifications more often accompany plaques that are still active. The test mainly measures the overall extent of the disease, which explains its prognostic value.

Calcium score and cardiovascular risk: what the studies show

The calcium score predicts heart attacks and strokes better than traditional risk factors, in every population studied. In the US MESA cohort, 6,722 adults without heart disease were followed for a median of 3.8 years. Compared with a score of zero, the risk of a coronary event was 7.73 times higher between 101 and 300, and 9.67 times higher above 300 (Detrano et al., 2008).

The 10-year follow-up of MESA confirmed these gaps in 6,814 participants aged 45 to 84, with 500 cardiovascular events. Each doubling of the score raised risk by 14%, with risk factors held equal. This link did not vary by age, sex or ethnic background (Budoff et al., 2018).

The CAC-DRS classes come from a consensus of the Society of Cardiovascular Computed Tomography, which standardizes reports (Hecht et al., 2018). The top of the scale has no ceiling. Among 66,636 adults without symptoms, the 2,869 people above 1,000 had all-cause mortality 2.89 times higher than those with a score of zero, and a risk 1.71 times higher again than people between 400 and 999 (Peng et al., 2020).

At the other end, a zero score is the most powerful reassuring signal known in prevention. Among 13 “negative” markers compared in MESA (low CRP, carotid arteries free of plaque, no family history), a zero score lowered estimated risk the most (Blaha et al., 2016). In 9,715 people followed for 14.6 years, a score of 0 guaranteed annual mortality below 1% for nearly 15 years in people at low or intermediate risk (Valenti et al., 2015).

These results come from observational studies: the CAC score identifies a risk, it does not prove that acting on this number saves lives. The only large randomized screening trial, DANCAVAS, invited 16,736 Danish men aged 65 to 74 to a checkup including this scan. After 5.6 years, all-cause mortality was not significantly reduced (12.6% versus 13.1%, HR 0.95), but strokes fell by 7% (Lindholt et al., 2022). Systematic screening of the whole population is therefore not justified to date.

Calcium score by age: how to read your number

Coronary calcium increases steadily with age, and it is higher in men than in women of the same age. That is the conclusion from 6,110 MESA participants analyzed by age, sex and ethnic background (McClelland et al., 2006). A score of 50 therefore does not mean the same thing at 42, where it places the person among the most calcified for their age, and at 72, where it remains modest.

For this reason, cardiologists read the result in two ways: as an absolute value (0, 100, 300) and as a percentile. The percentile compares your number with that of people of the same age, sex and ethnic background. The MESA researchers provide an online calculator for physicians. A score above the 75^th percentile signals faster arterial aging than average, even if the absolute value looks low.

In young adults, the slightest trace of calcium carries considerable weight. In the CARDIA study, 3,043 participants with an average age of 40 had a scan. Those with a positive score had a 5.0-fold higher risk of a coronary event over 12.5 years. Above 100, the risk of death was 3.7 times higher (Carr et al., 2017).

Conversely, after 70, a zero score becomes rare and highly informative. The Valenti study translates this result into “vascular age”: a score of 0 corresponds to arteries 1 year younger between 50 and 59, 10 years younger between 60 and 69, 20 years younger between 70 and 79 and 30 years younger after 80. This notion speaks to people more than a percentile does, but it remains a statistical estimate.

Calcium score in practice: who it is for and why

The CAC score is most useful when it can change a decision, particularly whether or not to take a statin. The 2018 US cholesterol guidelines propose it for adults aged 40 to 75 whose calculated risk is intermediate and whose treatment choice remains uncertain (Grundy et al., 2019). The 2021 European guidelines consider it for reclassifying people close to a decision threshold (Visseren et al., 2021).

This link with treatment rests on concrete data. In 13,644 patients followed for 9.4 years at Walter Reed, statin use was associated with 24% fewer events in people with coronary calcium, but with no measurable benefit in the absence of calcium. With a score of 1 to 100, 100 people had to be treated to prevent one event over 10 years, compared with 12 above 100 (Mitchell et al., 2018).

This scan complements blood work; it does not replace it. To put your other numbers in context, see our article on what cholesterol reveals about longevity and the one on the blood pressure number that should raise a flag. The role of inflammation in blood vessel aging is detailed in our pillar page on altered intercellular communication.

Radiation exposure remains low. Across 3,442 MESA exams performed on modern scanners, the average effective dose was 1.05 mSv (Messenger et al., 2016). That is roughly a few months of natural background radiation. The test is of no use in someone already followed for coronary disease, nor in case of chest pain, which calls for prompt medical attention.

What to do depending on your calcium score

The score is not treated in itself: it is the factors feeding the plaques that can be corrected. No supplement makes coronary calcium disappear. In the AVADEC trial, 365 men with an average age of 71 received 720 µg of vitamin K2 and 25 µg of vitamin D daily for 24 months. Progression of coronary calcium did not differ from placebo (Diederichsen et al., 2022). Our guide to vitamin K2 reviews what it actually delivers.

The benchmarks below summarize the usual approach, to be discussed with your doctor:

• Score of 0: 10-year risk is low, lifestyle remains the foundation, and a repeat scan is not useful for several years.
• Score of 1 to 99: the statin discussion mainly arises after 55 or when other risk factors are present.
• Score of 100 or more, or above the 75^th percentile for age: the 2018 US guidelines consider lipid-lowering treatment generally justified.
• Score above 1,000: the risk profile approaches that of people who have already had a heart attack, with dedicated cardiology follow-up.
• Smoking: quitting remains the most rewarding step, whatever the number.

A CAC score that rises on a statin is not a sign of failure. An analysis of 8 intravascular ultrasound trials showed that high-intensity statins reduced plaque volume while increasing plaque calcification (Puri et al., 2015). A more calcified plaque is generally more stable. Repeating the scan to “check” the effect of treatment therefore makes little sense.

Physical activity keeps its full place, including in highly trained athletes. In 284 men aged 55, the highest exercise volumes came with more coronary calcium (68% versus 43%), but fewer mixed plaques, considered more fragile (48% versus 69%) (Aengevaeren et al., 2017). In the Cooper Center Longitudinal Study, among 21,758 men, this very active profile did not increase mortality over 10.4 years, even with a score of 100 or more (DeFina et al., 2019).

Cardiovascular diseases remain the leading cause of death worldwide, with 19.8 million deaths in 2022 (32% of all deaths) according to the World Health Organization, which points out that most are preventable by controlling risk factors. To receive our next analyses on artery health, sign up for our health newsletter.

Frequently asked questions about the calcium score

What is a normal calcium score for my age?

There is no single normal value. Before 45, the expected score is 0, and any calcium is abnormal for that age. After 60, a low score is common, especially in men. Ideally the report should give a percentile: above the 75th percentile for your age, sex and ethnic background, arterial aging is faster than average.

Does a calcium score of zero mean my arteries are healthy?

A calcium score of zero means there is no calcified plaque, which is very reassuring: in MESA, the 10-year risk of a cardiovascular event stayed below 5.6%. It does not rule out soft, non-calcified plaque, which is more common in smokers and younger people. In a person at low or intermediate risk, this result keeps its value for several years.

Why does the calcium score go up on a statin?

Statins stabilize atherosclerotic plaques by making them denser in calcium. An analysis of 8 trials published in 2015 showed a reduction in plaque volume on high-intensity statins, alongside an increase in their calcification. A score that rises on treatment therefore does not mean the statin is ineffective, and this number is not used to monitor treatment.

Is the calcium score scan dangerous?

The test involves a low dose of X-rays. In the MESA cohort, the average dose measured across 3,442 modern scans was 1.05 mSv, or a few months of natural background radiation. It requires no injection and no special preparation. This dose nevertheless justifies not repeating the test without reason, and reserving it for situations where it can change a prevention decision.

Can you lower your calcium score?

Coronary calcium does not disappear, and no supplement has lowered the score in a rigorous trial: vitamin K2 combined with vitamin D failed in the AVADEC trial in 2022. The realistic goal is to slow plaque progression and prevent a heart attack by acting on LDL cholesterol, blood pressure, smoking, diabetes and physical activity.