Scientists have identified a common genetic mutation that raises the risk of aneurysms – the life-threatening bulges in arteries that kill thousands of people in Britain alone each year. The finding could help unravel why aneurysms form in the aorta, the largest artery in the body, and what causes them to grow to a size that makes them likely to rupture.

The disease is most common in white, middle-aged men and often goes unnoticed because aneurysms rarely cause obvious symptoms until they burst and trigger massive internal bleeding.

People who smoke and have high blood pressure are more at risk of aortic aneurysms, but the disease also runs in families, suggesting that genes play a significant role in the condition.

A team led by Matt Bown, a vascular surgeon at Leicester University in the UK, compared the genetic makeup of 1,866 patients with abdominal aortic aneurysms with a healthy group of 5,534 people. Gene sequences that appeared more often in the aneurysm patients were then confirmed in several thousand other patients.

In a study published in the American Journal of Human Genetics, the team describe a variant of a gene called LRP1 that was more common in patients with aneurysms than the healthy control group. The gene has piqued scientists' interest because it is not known to be associated with coronary heart disease, high blood pressure or any other conditions that affect blood supply.

They found that 38% of white Europeans carry two copies of the mutated LRP1 gene, one from each parent, leading to a 14% higher risk of an abdominal aortic aneurysm. For men aged over 65, that raises the chances of an aneurysm from around 5% to 5.7%.

The discovery will not help in efforts to screen people for risk of aortic aneurysms, but instead will shed light on the biological mechanisms that cause the dangerous swellings to form.

"This gives us a target to look at to work out what causes these aneurysms to grow. If we can do that, we can hopefully find ways to stop them growing and prevent people from needing operations," Bown told the Guardian.

The LRP1 gene is known to regulate an enzyme called MMP9 that breaks down blood vessel walls, but it is unclear precisely how the gene variant affects aneurysms. The risk-raising mutation is less common in South Asian populations, who rarely develop aneurysms, but more common in African Americans, who are also less affected by the disease than white populations.

In early 2013, the NHS expects to be screening all 65-year-old men in England for aortic aneurysms using ultrasound scans. Screening staff will monitor the size of any small aneurysms they find but patients with aneurysms at least 5.5cm wide, when they are at risk of bursting, will be referred to a consultant vascular surgeon.

Some 4,000 people a year in the UK have surgery to treat aortic aneurysms, which involves inserting a cylindrical stent into the aorta, but according to the British Heart Foundation, the condition still kills an estimated 7,000 a year.

"Aortic aneurysms tend to run in families, so we've realised for some time that there's likely to be a genetic component to the condition but it's not as yet clear what this is," said Shannon Amoils, research adviser at the British Heart Foundation.

"What we don't yet know is why this DNA variant is associated with the condition, and the next step for researchers is to decipher this. Understanding more about the biology behind this link may help to uncover how aneurysms develop and lead to clues to how we could prevent them and save lives."

• This article was amended on 4 November 2011. The original stated that the NHS screening programme would start in 2013 and that doctors would carry out the screening. This has been corrected.