A test that determines whether people have an inherited vulnerability to heart attacks is to be developed after scientists discovered a genetic variant that can double the risk of having one at an early age.

The DNA test, which is being developed by an Icelandic company, has been assisted by two separate studies that identified a genetic profile that increases a person’s susceptibility to heart attacks and coronary heart disease.

The most damaging variant, which is carried by between a fifth and a quarter of the white European population, raises the chances of a heart attack, at any age, by up to 60 per cent.

In early middle age, it has an even greater impact: it doubles the risk for men younger than 50, and for women younger than 60, researchers found.

Coronary heart disease is the biggest cause of death in developed countries such as Britain.

In England, about 275,000 people have a heart attack each year, and 110,000 people die of heart disease.

While many other factors, particularly diet, exercise and smoking, have a greater impact on the risk than genes, the discovery should eventually allow doctors to identify patients with a high genetic vulnerability.

They could then be advised to change their lifestyle accordingly, to reduce the risks, or treated at an earlier stage with cholesterol-lowering drugs such as statins.

In the longer term, insights into how the genetic variant increases risk might also be used to assist the design of new drugs.

The Reykjavik-based biotechnology company deCODE Genetics, which conducted one of the studies, said that it now intends to develop a test that would incorporate other genetic variants that contribute to heart attacks.

It said in a statement: “deCODE plans to bundle this discovery with other genetic variants it has linked to risk of heart attack into a DNA-based test for gauging inherited risk of myocardial infarction [heart attack].

“The company believes that such a test, particularly for those with other risk factors, may enable individuals and their doctors to adopt more informed and thus potentially more effective prevention regimes.”

Ruth McPherson, director of the University of Ottawa Heart Institute in Canada, who led the second study, said: “If we can identify genetic factors which influence heart disease risk, over and above known risk factors, we can do a better job of identifying those people who will benefit most from early intervention to reduce their risk.”

The two studies, which are published in the journal Science, scanned hundreds of thousands of single-letter DNA spelling mistakes known as single nucleotide polymorphisms (SNPs, pronounced “snips”), in search of variants that might be linked to heart attacks.

Both alighted on an SNP that lies close to two genes called CDKN2A and CDKN2B. Each person inherits two copies of this stretch of DNA, one from each parent. When people inherit two copies of the SNP variant, they have a subtantially higher risk of heart disease than those with two normal copies.

The Icelandic study found an increased risk of around 60 per cent, while the Canadian researchers put their risk at 30 to 40 per cent higher. One normal copy paired with one copy of the variant raised the risk by 15 to 20 per cent.

The deCODE study also looked at the risk of early heart attacks, before the age of 50 in men and 60 in women. It found that two copies of the variant doubled the risk, while one copy increased it by 49 per cent.

Independent researchers welcomed the findings. However, they cautioned that it is likely to take some time before genetic tests are developed or used in clinics. Genes remain less important than lifestyle factors in the onset of heart disease, they said.

Professor Peter Weissberg, Medical Director of the British Heart Foundation (BHF), said: “Trying to find genes that put some families at an increased risk of heart attacks is like trying to find a collection of needles scattered amongst a field full of hay stacks.

“The significance of these two studies is that two independent research teams have homed in on the same hay stack – a region of DNA within chromosome 9.

“This makes it very likely that they are close to identifying a needle – an important gene in that region.

“However, this will take a lot more research and – once found – the gene will be only one of several factors that are important. This research represents an important step along a very long journey, but a step in the right direction.”

Tim Chico, of the University of Sheffield, said: “This is very interesting scientifically, but it won't change the way patients are investigated or treated at the moment.

“We must not forget that 90 per cent of the risk of a heart attack comes from things like smoking, cholesterol, diet, lack of exercise and diabetes.

“Whatever our genetic make-up, we can all reduce our chances of heart disease by improving our lifestyle.”

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