Recent research indicates that individuals with type A blood may have a higher likelihood of experiencing a stroke before the age of 60 compared to those with different blood types. Blood types are determined by specific chemicals found on the surfaces of red blood cells, with the main types being A, B, AB, and O.

A study published in 2022 by genomics researchers highlighted a significant association between the A1 subgroup gene and early-onset stroke. This research analysed data from 48 genetic studies involving approximately 17,000 stroke patients and nearly 600,000 controls, all aged between 18 and 59.

Key Findings of the Study

The genome-wide search identified two locations linked to an increased risk of early stroke. One of these locations coincided with the genes responsible for blood type. Further analysis of specific blood-type genes revealed that individuals with a variation of the A group had a 16 percent higher risk of stroke before 60. Conversely, those with the O1 blood type had a 12 percent lower risk.

Despite these findings, researchers noted that the additional risk associated with type A blood is minimal, suggesting that enhanced vigilance or screening for this group may not be necessary. Senior author Steven Kittner, a vascular neurologist from the University of Maryland, remarked on the unknown factors behind this increased risk. He speculated that it may relate to blood-clotting factors or proteins involved in clot development.

Contextualising the Results

While the implications of blood type on early stroke risk are intriguing, it’s important to contextualise these results. In the United States, nearly 800,000 strokes occur annually, predominantly affecting individuals aged 65 and over. The study’s participants were primarily from North America, Europe, Japan, Pakistan, and Australia, with only 35 percent being of non-European descent, indicating a need for further studies with more diverse populations.

The research also compared individuals who experienced a stroke before and after 60. In the later-onset group, the heightened risk for those with type A blood diminished, suggesting that early strokes may arise from different mechanisms than those occurring later in life.

Conclusion: Implications for Future Research

Additionally, individuals with type B blood were found to be approximately 11 percent more likely to experience a stroke compared to controls, regardless of age. Previous research has linked the genetic region coding for blood type to coronary artery calcification and a higher risk of venous thrombosis.
The study underscores the need for further investigation into the mechanisms behind the increased stroke risk associated with specific blood types, particularly in younger populations.