Research has uncovered a significant association between blood type and the risk of experiencing an early stroke, particularly among individuals with type A blood. This finding, published in the journal Neurology in 2022, sheds light on how genetic factors can influence stroke vulnerability before the age of 60.
In a comprehensive analysis, researchers reviewed data from 48 genetic studies, which included approximately 17,000 stroke patients and nearly 600,000 non-stroke controls. All participants were aged between 18 and 59. The study indicated a clear link between the A1 blood subgroup and an increased risk of early-onset stroke. According to Mark Gladwin, a physician-scientist at the University of Maryland, “This important and surprising research finding adds to our current knowledge about non-modifiable risk factors for stroke – including a person’s blood type.”
The research identified two genomic locations strongly associated with early stroke risk. One of these locations aligns with the genes responsible for blood type. Further analysis revealed that individuals with genetic coding for the A group had a 16 percent higher chance of suffering a stroke before turning 60 compared to those with other blood types. Conversely, those with the O1 blood type exhibited a 12 percent lower risk.
Despite these findings, the researchers emphasized that the additional risk for individuals with type A blood is relatively small, meaning there is no immediate need for heightened screening or vigilance for this group. Steven Kittner, a senior author and vascular neurologist at the University of Maryland, noted, “We still don’t know why blood type A would confer a higher risk, but it likely has something to do with blood-clotting factors like platelets and cells that line the blood vessels.”
While the implications of such a discovery may seem alarming, context is crucial. In the United States alone, nearly 800,000 individuals experience a stroke each year, with the majority occurring in those aged 65 and older. The risk of stroke doubles every decade after the age of 55. Moreover, the participants in this study were predominantly from North America, Europe, Japan, Pakistan, and Australia, with only 35 percent having non-European ancestry. Future research with a more diverse sample may further elucidate these findings.
The study also highlighted differences between early-onset and late-onset strokes. Researchers compared nearly 9,300 individuals who had a stroke after the age of 60 with around 25,000 controls. They found that the heightened stroke risk associated with type A blood was not significant in the late-onset group, indicating that early strokes may have distinct underlying mechanisms compared to those that occur later in life. For younger individuals, strokes are less likely to stem from atherosclerosis, a condition characterized by fatty deposits in the arteries, and are more often linked to clot formation.
Additionally, the study found that individuals with type B blood were approximately 11 percent more likely to experience a stroke compared to non-stroke controls, irrespective of age. Previous research has indicated that the genomic region coding for blood type, known as the ABO locus, is associated with coronary artery calcification and an increased risk of heart attacks. Genetic sequences associated with A and B blood types have also been linked to a slightly elevated risk of venous thrombosis, a condition involving blood clots in veins.
In conclusion, while this research offers new insights into the relationship between blood type and stroke risk, experts like Kittner stress the necessity for follow-up studies to fully understand the mechanisms behind these findings. As stroke remains a leading health concern globally, such investigations could inform future preventative strategies and clinical practices.
