Research chief Nadeem Qureshi, a professor at the University of Nottingham and a practising GP, said around half are not reaping the rewards of the wonder drug.
“Up to three million people remain at greater risk of a heart attack because their cholesterol levels are not dropping as much as is needed,” he said.
“If you’re at a high risk of heart disease and you take them as prescribed you can lower your risk of heart attacks dramatically, by as much as 20 per cent. There’s a definite benefit.
“If you stop when you should be taking them then you’re increasing your risk of a heart attack.”
A landmark review led by the University of Oxford’s Professor Sir Rory Collins in 2016 claimed the drugs prevent around 80,000 heart attacks and strokes a year in the UK.
However, doctors fear patients are at risk because they are failing to take the medicine at the recommended dosage and for the duration of the course prescribed.
Earlier this year, a major study by Stanford University of 350,000 patients with heart disease found those who failed to take their statins correctly were three times more likely to die within a year.
Identify The drugs help lower the level of LDL cholesterol in the blood. This prevents the build-up of fatty deposits in the arteries, slashing the risk of heart disease or stroke.
Clinical trials have shown statins were extremely effective at achieving the National Institute for Health and Care Excellence’s target 40 per cent drop in cholesterol.
But many drugs do not achieve the same results outside of a trial setting.
To evaluate the real world success of statins, researchers in the latest study analysed data from the UK Clinical Practice Research Data Link, along with statistics on hospital treatments and causes of death.
The 165,000 patients studied had an average age of 62 when first prescribed statins from 1990 to 2016 – but just 49 per cent achieved the target drop in cholesterol.
Lead study author Professor Stephen Weng said: “What we didn’t expect is half of individuals don’t achieve the 40 per cent target reduction in LDL cholesterol. That has significant consequences for their risk of heart disease. It could be patients not adhering [to taking the drugs as prescribed] or the dosage is incorrect. “There is also genetic variation in how patients respond to treatments.”
After adjusting for factors including age and any ailments before treatment, patients who missed the target were 22 per cent more likely to develop heart disease than those who slashed their cholesterol.
Professor Helen Stokes-Lampard, Chair of the Royal College of GPs, said “statins are safe and effective” for most people. But she added: “We have to rely on patients to make sure they take it, at the recommended dose and for the duration of time that we think will benefit them most.
“We encourage anyone on regular medication to attend their medication reviews and raise any concerns.”
Researchers said better education for doctors and patients could help people improve their cholesterol.
Dr Weng said screening patients before giving a prescription could also help doctors identify the best drug for them.
But Kausik Ray, a professor at Imperial College London, said there was not enough evidence such tests were needed.
The study was in the journal Heart.