Study Links Blood Type to Early Stroke Risk: Type A May Face Increased Odds

A recent study indicates a potential correlation between blood type and the likelihood of experiencing a stroke before the age of 60. The research suggests individuals with blood type A may face a slightly elevated risk, while those with blood type O may have a reduced risk.

Approximately 15 million individuals globally experience a stroke annually, according to the World Health Organization (WHO). Of these, 5 million are fatal, and another 5 million result in permanent disability. Strokes can be devastating. But, according to new research, your risk of having a stroke may be written in your blood type.

A new meta-analysis, spearheaded by researchers at the University of Maryland School of Medicine (UMSOM), proposes that blood type could serve as a predictor of stroke risk before the age of 60. This finding could pave the way for innovative strategies to predict and prevent strokes in younger adults. The research has been published in the journal Neurology.

What is a Stroke?

A stroke occurs when blood flow to the brain is interrupted, either by a blockage or sudden bleeding. There are two primary types of strokes:

• Ischemic stroke: Occurs when blood flow to the brain is blocked.
• Hemorrhagic stroke: Occurs when a blood vessel ruptures and bleeds into the brain.

Ischemic stroke is the more prevalent type, accounting for approximately 87% of all stroke cases.

Blood Type and Stroke Risk

The recent study reveals a potential link between a person’s blood type and their risk of experiencing an early stroke.

The meta-analysis encompassed data from genetic studies focused on ischemic strokes in adults under 60.

According to study co-principal investigator Steven J. Kittner, MD, MPH, Professor of Neurology at UMSOM, the incidence of early strokes is increasing. He notes that these individuals face a higher risk of mortality and potential long-term disability.

Kittner and his team conducted a meta-analysis of 48 studies on genetics and ischemic stroke, involving 17,000 stroke patients and nearly 600,000 healthy individuals without a history of stroke. The researchers investigated genetic factors associated with early strokes and identified variations that could explain higher risks in certain individuals.

The findings indicated that individuals with early stroke were more likely to have blood type A and less likely to have blood type O, compared to those with late stroke and those who had never experienced a stroke. Both early and late stroke patients were also more likely to have blood type B compared to the control group. The study revealed that individuals with blood type A had a 16% higher risk of early stroke compared to other blood types, while those with blood type O had a 12% lower risk.

Expert Opinions

Study co-principal investigator Braxton D. Mitchell, PhD, MPH, Professor of Medicine at UMSOM, stated that the meta-analysis examined people’s genetic profiles and found associations between blood type and the risk of early-onset stroke. He noted that the association between blood type and later-onset stroke was much weaker than that found with early stroke.

The researchers emphasized that the increased risk was modest and that individuals with blood type A should not be overly concerned about experiencing an early-onset stroke or undergoing extra screening or medical testing based on the study's findings.

Dr. Kittner added that the reasons behind the higher risk associated with blood type A are still unknown, but it may be related to blood-clotting factors such as platelets, cells lining the blood vessels, and other circulating proteins involved in blood clot development. He emphasized the need for further studies to clarify the mechanisms underlying the increased stroke risk. Previous research has also suggested that blood type A is associated with a slightly higher risk of developing blood clots in the legs, known as deep vein thrombosis.

The researchers concluded that the study raises an important question requiring further investigation into how genetically predetermined blood type may influence early stroke risk, highlighting the urgent need to discover new ways to prevent these potentially devastating events in younger adults.