Researchers have identified a genetic variation that may raise the risk for stroke by affecting brain cells’ ability to respond to injury.
Stroke is the third leading cause of death in the United States, striking almost 800,000 people each year. High blood pressure, high cholesterol, smoking, diabetes, obesity and a history of cardiovascular disease can all increase the risk of having a stroke, but studies of families and twins indicate that genes play a substantial role too. So far, however, the genes underlying stroke risk in the general population remain undetermined.
Scientists combined data from several large studies comprising almost 29,000 people from the United States and the Netherlands to look for genetic variations associated with stroke risk. Their results, published online today in the New England Journal of Medicine, link a region of the genome not previously associated with stroke to increased risk in both black and white populations.
Strokes can be either hemorrhagic (caused by a broken blood vessel that bleeds into or around the brain) or ischemic (caused by a blood clot that blocks blood flow to the brain). Most strokes are the ischemic type.
Combined analysis of data from Caucasian study participants from the United States and the Netherlands revealed that the A version of this SNP is associated with a 1.29 times increased risk of ischemic stroke. The SNP was also associated with an increased risk for ischemic stroke in a large African American study group — 1.42 times for each copy of an A. Analysis of a smaller group of African Americans failed to yield a significant association between and stroke.
The risk of stroke is almost doubled for African Americans compared to white Americans, and African Americans are more likely to die from stroke or complications from stroke than any other ethnic group. This SNP is located near the NINJ2 gene, which encodes a protein that has been implicated in nerve cell injury response in animal studies. Several other SNPs in and around the NINJ2 gene showed modest association with stroke. The authors of the study suggest that SNPs affecting how much protein is made from the NINJ2 gene might influence the brain’s response when deprived of oxygen by a blood clot.