Researchers have identified a direct connection between the gene for the A1 subgroup and the occurrence of stroke at an early age.
A total of 48 genetic studies were analyzed by the researchers, and the participants included almost 17,000 persons who had suffered a stroke and nearly 600,000 controls who had not suffered a stroke. Age ranged from 18 to 59 for all of the participants in this study.
Two locations on the genome were found to be strongly related with an earlier risk of stroke after a genome-wide search. One of them coincided with the location of the genes that determine blood type.
People whose genomes coded for a variation of the A group had a 16 percent increased risk of having a stroke before the age of 60, according to the findings of a second study that focused on certain blood-type genes. This was compared to the risk of stroke among people with other blood types.
Those individuals who possessed a gene for group O1, which reduced the risk by 12 percent,
The researchers did note, however, that the elevated risk of stroke among those who have type A blood is rather low; hence, there is no requirement for any additional monitoring or screening in this population.
"We still don't know why blood type A would confer a higher risk," senior author and vascular neurologist Steven Kittner said.
"But it likely has something to do with blood-clotting factors like platelets and cells that line the blood vessels as well as other circulating proteins, all of which play a role in the development of blood clots."
In spite of the fact that the findings of the study would appear to be cause for concern - namely, the suggestion that blood type might influence the early stroke risk - let's put these results in perspective.
In the United States, little under 800,000 people will suffer from a stroke on any given year. The majority of these occurrences, almost three out of every four, take place in adults aged 65 and older, and the risk of developing one of these conditions doubles every decade beyond the age of 55.
In addition, the participants in the study were from all over the world, including North America, Europe, Japan, Pakistan, and Australia; nevertheless, only 35% of the individuals were of an ethnic background other than European. The significance of the findings might be easier to understand if subsequent research utilized a participant pool that was more demographically diverse.
Previous research has suggested that the region of the genome known as the "ABO locus," which is responsible for coding blood types, is linked to coronary artery calcification. This condition reduces blood flow and increases the risk of heart attack.
The genetic sequence that determines blood types A and B has also been linked to an increased likelihood of developing venous thrombosis, which is a condition in which blood clots form in the veins.
This research was published in the journal Neurology.
