Mygripe SCIENTISTS have found a genetic explanation for why men are more likely than women to suffer heart attacks and strokes.

The British team found a cluster of genetic variants on the male sex chromosome that puts carriers at an increased risk of heart disease.

Previously, the difference between the rate of heart disease for men and women was attributed to men being more likely to have “high-risk” lifestyles – by smoking, for example – and to the protective effect on the heart of the female hormone oestrogen.

The latest study, presented at the European Society of Cardiology Congress in Stockholm, indicates that men who carry a set of genes – the I-haplogroup – on their Y chromosome are at 55 per cent greater risk of heart disease.

“We’re very familiar with this difference between men and women but it has been unclear whether it is to do with lifestyle, hormones or whether there is a genetic origin,” said Nilesh Samani, Professor of Cardiology at Britain’s University of Leicester and the lead author.

The finding also provides a tantalising explanation for why northern Europeans tend to be at greater risk of heart disease than their Mediterranean counterparts. The I-haplogroup is most prevalent in northern, central and eastern Europe, suggesting that genetics as well as a diet and lifestyle may play a role.

In future, doctors could take into account this risk factor, alongside cholesterol and blood pressure, to help identify those individuals at greatest risk.

“As a man I would want to have this test,” said George Kassianos, a GP with a special interest in cardiology, based in Berkshire in England. “As a doctor, if someone was already at risk and they had these gene variants as well, I could put them on statins sooner.”

The scientists behind the study said that it would be necessary to establish the mechanism by which the genetic variants increased a person’s risk before pre-emptive genetic tests would be clinically useful.

However, they cautioned that direct-to-consumer testing companies were likely to jump on the findings and add the I-haplogroup to the portfolio of risk factors that could be disclosed through personal genetic tests.

“They’re giving out information that we don’t yet understand properly, let alone know what to do about,” said Peter Weissberg, medical director of the British Heart Foundation, which funded the study.

While women have two X chromosomes, men have one X and one Y, and the Y is always inherited from their fathers. As it is never paired with a partner, it escapes a process called recombination that shuffles the code of every other chromosome in each new individual. It is thus transmitted almost intact in the male line from generation to generation, altered only by rare spontaneous mutations.

These mutations can be used to identify categories of Y chromosome, known as haplogroups. Men from the same haplogroup must have shared a common male ancestor in the past. The I-haplogroup can be traced back to the Gravettian culture, which arrived in Europe from the Middle East about 25,000 years ago.

In the study, 3,000 males were tested, including 1,295 with heart disease. Those carrying the I-haplogroup variant had a 55 per cent higher risk of the disease. The association was not explained by traditional risk factors such as cholesterol, high blood pressure or smoking. “This study could explain to a large degree what predisposes men to heart disease,” Professor Weissberg said.

The scientists are working to identify the specific genes involved and the biological mechanisms by which they increase risk. Studies are also planned using data from other European countries to determine the extent to which the I-haplogroup explains the lower incidence of heart disease in Mediterranean countries.

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