Two genetic variants linked to an increased risk of ischemic stroke, the third leading cause of death in the United States, have been identified for the first time in a study released Wednesday.
The findings, published online by The New England Journal of Medicine, open the way to treat the pathology by identifying molecular mechanisms underlying stroke risks, researchers said.
"As we learn more about the role that an individual's unique genetic makeup plays in their overall health, we will ultimately be able to tailor care to better diagnose, prevent, and treat conditions such as stroke," said National Heart, Lung and Blood Institute (NHLBI) director Elizabeth Nabel.
The researchers found that two previously unsuspected common genetic variants, or single-nucleotide polymorphisms (SNPs) were consistently linked with ischemic stroke and all types of total stroke in white individuals.
Based on analysis of data from four genome-wide studies in the United States and Europe, the researchers found that about 20 percent of white and 10 percent of blacks have at least one copy of a genetic variant associated with increased risk of ischemic stroke.
Each copy of the variant increased the risk of ischemic stroke by approximately 30 percent, the study said.
"The risk of stroke associated with these SNPs is not sufficiently high to make an individual change their stroke prevention plan," cautioned Walter Koroshetz, deputy director of the National Institute of Neurological Disorders and Stroke (NINDS), which helped fund the study.
"However, the results will lead scientists to direct their attention to new, important biologic mechanisms and hopefully new treatments to prevent stroke."
Nearly 90 percent of all strokes are ischemic strokes, which are caused by blocked blood vessels in the brain. The other 10 percent are due to brain hemorrhage.
Over 150,000 Americans die from stroke every year, making it the third leading cause of death after cardiovascular disease and cancer.
"Discovering genes for stroke has been a challenge in part because there are many different types of stroke," said Christopher O'Donnell, senior advisor for genome research to the director of NHLBI, which funded the study through grants and contracts.
"These results provide strong evidence for a previously unknown gene that may predispose to stroke and suggests that more genes will be discovered -- improving our chances of reducing the toll from this important public health problem."
The study "gives us a pointer or a beacon on the genome where we can look further," explained Myriam Fornage, one of the study's lead authors.
Scientists linked two variants to an increased risk of ischemic stroke by comparing the genomes of 1,544 individuals who developed stroke with those of 18,058 individuals who did not develop stroke. The findings were then replicated in separate studies of blacks and whites.
Comparative genome studies are a relatively new research tool that allows scientists to quickly scan the genomes of a large number of people in order to identify genetic variations or defects linked to particular diseases.
This technique has revealed a significant number of links between specific genetic variations and diseases like adult, or type 2 diabetes and heart disease.
The first complete human genome was published in 2003, by the Human Genome Project, at an estimated cost of around 300 million dollars.