Does the blood type predict early stroke risk?

A person's blood type may be linked to how likely they are to have an early stroke, according to a new meta-analysis of more than 600,000 patients in 48 studies. Published in Neurology August 31, the findings included all the data that was available from genetic studies regarding ischemic strokes. These are a form of brain damage caused by blockage or blood supply. According to the Centers for Disease Control and Prevention, this kind of stroke is responsible for 87 percent in the population.

"The number of people with early strokes is rising," said the study's co-principal investigator Steven J. Kittner, MD, MPH, in a press release. Kittner, a neurology professor at UMD School of Medicine in Baltimore. This group is more at risk for death from life-threatening events, with survivors facing decades of disability. However, little is known about the causes of strokes in early stages.

A paper in Stroke's February 2020 issue estimates that 10-15 percent of strokes happen in those under 50.

People with Type A Blood are more likely to have early onset strokes

Researchers analyzed 48 studies about genetics and stroke. These included patients who suffered from stroke and healthy controls (never having had one) that examined how genes could affect stroke risk.

Researchers discovered a connection between strokes that occur before the age of 60 and an area on the chromosome that contains the gene that decides whether a person's blood type is O, AB, B or B.

The study found that people who experienced an early stroke were more likely to have blood type A and less likely to have blood type O than people with late stroke and people who never had a stroke.

People who suffered from both late and early strokes were more likely than those in the healthy controls to be of blood type B. Researchers found that people who were blood type A had an 16% higher chance of having strokes before they had any other types of people. People with blood type O had a 14% lower risk.

The authors found that the association between blood type and later-onset stroke was weaker than that with early stroke.

This an interesting study, says Brandon Giglio, MD, the director of vascular neurology at NYU Langone Hospital in Brooklyn, New York, who was not involved in the study. Research has suggested that blood type may also be associated with other clotting disorders such as deep vein embolisms and pulmonary embolisms.

A study published in January 2020 in the American Heart Association journal Arteriosclerosis, Thrombosis, and Vascular Biology compared people with type O blood and those with type A or B blood and found the latter were 51 percent more likely to develop deep vein thrombosis and 47 percent more likely to develop a pulmonary embolism.

Dr. Giglio states, "It's fascinating that this association applies to these types clots in arteries rather than those which are found in veins. Though different mechanisms or processes cause strokes from those other types, it is still interesting." These findings show that there may be a correlation between the patient’s blood type, and the body’s ability to promote the formation of clots.

101 Blood Types

Your blood types can be determined by your level of specific antigens. Antigens are substances which trigger an immune reaction to foreign "invaders".

Additional Screening Due to Blood Type is Not Necessary

Researchers stressed the fact that this increased risk is very small and people of type A blood shouldn't be worried about developing strokes early in life.

Giglio also agrees. He says, "With what information we currently have, I don’t think there are any interventions that can modify risk based blood type," he states.

How to reduce your risk of getting a stroke

Giglio says that regardless of your blood type, there are clear ways to lower stroke risk.

These healthy lifestyle recommendations are recommended by the CDC.

A healthy diet low in trans fats, saturated fats, cholesterol, and high in fruits and vegetables is a good choice.

Keep a healthy weight. Keep fit by following the recommendations for exercise and completing at least two hours of moderate-intensity activity each week.

Avoid smoking and drink less alcohol.

Consider vascular risk factors, such as high cholesterol and blood pressure.

Scientists Hope That These Results Will Help Prevent Strokes in Younger Adults

Kittner says, "We need to do more research in order to understand the mechanism of stroke risk."

The authors also acknowledge that the current study is limited by a "relative lack of diversity among participants."

Giglio states that future research might look at whether there is a link between risk factors for strokes and blood types. He suggests that it could be possible that a particular blood type can put people at greater risk for certain diseases, which in turn increases their risk of suffering strokes, like diabetes and obesity.