The study, the first to identify a chromosomal region containing common genetic variants responsible for an increased risk of ischemic stroke, has found important genetic differences that significantly raise the risk of stroke in millions of people, which may lead to better treatments.

Eric Boerwinkle of The University of Texas Health Science Centre says, while other stroke-related genes have been discovered, none involved such a wide portion of the population.

Publishing the study in the New England Journal of Medicine, Boerwinkle says: 'This is a first step in unraveling the genetic contributions of this debilitating disease,' the third-leading cause of death in the US, causing serious long-term disabilities for many worldwide.

Boerwinkle and his team discovered two genetic variants on chromosome 12 near two genes implicated in stroke, of which WNK1 is associated with blood pressure control and NINJ2 linked with brain injury repair. Next to each other, the two genes are also strongly linked with ischemic stroke, the most common type of stroke caused by blocked blood vessels in the brain.

While, scientists are not clear about which specific gene is implicated, NINJ2 is considered to be the most likely suspect, as single nucleotide polymorphisms (SNPs) or two single-letter changes in the DNA near NINJ2, seem to send the strongest signal of stroke, 20% in whites and 10% in African-Americans. Just one copy of this genetic variation is enough to raise a 30% risk of ischemic strokes.

Scientists analysed the genetic code of over 19,000 people taking part in four long-term studies of cardiovascular risks in the United States and Europe, with teams looking for SNPs among 1,544-stoke patients, as compared to 18,058 people who had not had a stroke.

According to Boerwinkle, researchers need to understand how the genes work and identify the actual mutation that occurs in the gene, to figure out which genes are to blame. However, the findings should give drug companies a new target for researching better treatments and ways to prevent the most common type of stroke, by being able to identify people at greater risk for stroke, thus spurring more aggressive lifestyle changes to reduce that risk.