One in three of those put on statins because they are assessed to be at high risk of strokes and heart attacks may not need the drugs, research suggests.
A study published in the European Heart Journal suggests millions of patients put on the medications may be being “over treated” - exposing them to potential side effects - while other patients who are more likely to suffer a heart attack are not being targeted.
Most patients are put on statins because they have high cholesterol, high blood pressure or other conditions such as diabetes.
But the study of almost 7,000 adults found that the risk factors were not an accurate way of predicting the likelihood of a heart attack or a stroke.
Scans to examine the build-up of calcium in the arteries were far better at identifying patients who would suffer a cardiac event, researchers found.
The US study found that 35 per cent of those who were assessed as “very high risk” using conventional screening tools actually had an extremely low chance of having a heart attack.
Meanwhile, 15 per cent of those who were told they had a very low chance of such an event in fact were at far higher risk, which was indicated by high levels of calcium in the arteries.
Dr Michael Silverman, a cardiology fellow at Brigham and Women’s Hospital in Boston, said: “We showed that by using only the traditional risk factors, we miss a significant percentage of individuals at high risk.
“We may also be over-treating a large number of people who can safely avoid lifelong treatment.”
Researchers said coronary artery calcium (CAC) screening should play a more prominent role in helping determine a person’s risk for heart attack and heart disease-related death, as well as the need for angioplasty or bypass surgery.
Researchers said GPs should consider offering a coronary artery calcium scan to their patients to markedly improve risk prediction if they are unsure whether they should be on lifelong statin and aspirin therapy.
Watchdogs in this country are currently drawing up new guidance on statins, but said the new study had come too late to feed into their recommendations, which are likely tobe published in February.
CAC screening provides a direct measure of calcium deposits in heart arteries and is easily obtained on a computed tomography (CT) scan.
Professor of medicine Roger Blumenthal of the Johns Hopkins Ciccarone Center said: “We found that 15 per cent of people believed to be at very low risk actually had high coronary artery calcium scores above 100 and were at relatively high risk of a cardiac event over the next seven years.
“On the other hand, 35 per cent of study participants thought to be at very high risk and needing aggressive therapy with aspirin and statin medication actually had no coronary artery calcium and an extremely low event rate of the next seven years. For them, we can emphasise lifestyle modifications.”
In the study the researchers compared two approaches to risk assessment.
One approach looked only at risk factors including cholesterol, blood pressure, current smoking and diabetes.
The other used the direct measurement of atherosclerosis as seen on the coronary artery calcium score.
The study used data from almost 7,000 adult participants which allowed a more accurate, personalised assessment for those were either at high or low risk of a heart attack or death from coronary artery disease.
The study participants did not have evidence of heart disease when they joined the study between 2000 and 2002.
They were assessed for risk factors and had a coronary calcium scan and were followed for a mean of 7.1 years for coronary heart disease events, such as heart attacks.