Thousands of people are dying of heart attacks and strokes because life-saving drugs are being wrongly prescribed, doctors say.

More than a million patients in the UK are taking statins, the cholesterol lowering drugs which reduce the risk of heart attacks and strokes. But the drugs are being wrongly restricted to those with high cholesterol when thousands more lives could be saved if they were prescribed to everyone with diseased arteries.

The first comprehensive review of the cholesterol-lowering drugs called statins has found they can cut the risk of a heart attack or stroke by one third, if used in a big enough dose.

Colin Baigent, of the clinical trial service unit at the University of Oxford, who led the study, published in the online edition of The Lancet, said: "There aren't many drugs that can do that. Given a decent dose, statins are wonder drugs. [But] they are being used in a less than efficient wayt. What we have found is that if you are at high risk of a heart attack or stroke, reducing your cholesterol, regardless of its current level, will reduce your risk.'

"Many doctors use target levels for cholesterol. If you have an average cholesterol level you might get no statin or a low dose. Of those who are being treated with statins at least half are not getting a high enough dose.

"What matters most is that doctors identify all patients at risk of a heart attack or stroke, largely ignoring their blood cholesterol level, then prescribe a statin at a daily dose that reduces their cholesterol substantially. The goal of treatment should be to reduce cholesterol as much as possible. There is a problem of under-treatment."

The biggest benefits were in patients with the largest reduction in cholesterol, irrespective of their starting level before treatment. The review, a meta-analysis of 14 randomised trials of 90,000 patients, found the risk of a heart attack or stroke over five years was reduced by a fifth for every 1mmol reduction in the LDL (low density lipoprotein) cholesterol level. With the correct dose of statins, most people could reduce their cholesterol level by at least 1.5 mmols, achieving a one third reduction in their risk, the researchers said.

There was no evidence that statins increased the incidence of cancer, or that low cholesterol levels caused depression leading to suicide, two charges levelled against the drugs.

Professor Anthony Keech, of the University of Sydney who co-ordinated the study team in Australia said: "Statins are often prescribed in relatively small doses which may only reduce cholesterol modestly. Our results indicate that the benefits of statins appear directly proportional to the size of the reduction in cholesterol produced by treatment. So, bigger cholesterol reductions with more intensive treatment regimens should lead to greater benefits."

In the UK, six million people are estimated to be at high risk of a heart attack or stroke because they have had a cardiovascular event or are diabetic. A separate study of 90,000 elderly Americans, in Archives of Internal Medicine yesterday, found those taking statins had a 36 per cent lower risk of fractures.