A genetic² variant³ that increases the risk of a common type of stroke has been identified by scientists in a study funded by the Wellcome Trust and published online in Nature Genetics. This is one of the few genetic variants⁴ to date to be associated with the risk of stroke, and the discovery opens up new possibilities for treatment. Stroke is the second leading cause of death worldwide (causing more than one in ten of all deaths and more than six million deaths annually⁵, according to the World Health Organization) and is a major cause of chronic⁶ disability in high-income countries. As the world's populations age, the impact of stroke on wellbeing is likely to increase further.

Several different mechanisms⁸ underlie⁹ strokes. One of the most common types is when blood flow is impaired¹⁰ because of a blockage¹¹ to one or more of the large arteries¹² supplying blood to the brain -- large artery¹³（动脉） ischaemic stroke. This accounts for more than one-third of all strokes.

Researchers from St George's, University of London, and Oxford¹⁴ University, working with scientists from Europe, America and Australia in one of the largest genetic studies of stroke to date, compared the genetic make-up of 10 000 people who had suffered from a stroke with 40 000 healthy individuals.

The researchers discovered an alteration¹⁵ in a gene¹ called HDAC9 that affects a person's risk of large artery ischaemic stroke. This variant occurs on about 10 per cent of human chromosomes¹⁶. Those people who carry two copies of the variant (one inherited from each parent) have nearly twice the risk for this type of stroke than those with no copies of the variant.

The protein produced by HDAC9 is already known to have a role in the formation of muscle tissue and heart development; however, the exact mechanism⁷ by which the genetic variant increases the risk of stroke is not yet known. A better understanding of the mechanism could lead to new drugs to treat or prevent stroke, although the researchers stress that this is still some way off.

Professor Hugh Markus, from St George's, University of London, who co-led the study, says: "This discovery identifies a completely new mechanism for causing stroke. The next step is to determine in more detail the relationship between HDAC9 and stroke and see whether we can develop new treatments that reduce the risk of stroke.