One wouldn’t know it by glancing at anybody, yet our blood is divided into groups by small variances that run down our veins every second of each day: A+, A-, B+, B+, O-, O+, AB+, and AB-.

Once you’re in the hospital and require a blood transfusion, or after you’ve donated blood and discovered which kind you have, these minor changes normally don’t matter. Many people discover they have a negative blood type during childbirth when particular treatment is needed.

However, increasing research into blood type reveals that it may mean more than we thought, at least when it comes to determining risk for some health disorders, including heart disease. These imperceptible changes in blood may provide some people an advantage in avoiding cardiovascular diseases while making others more vulnerable.

WHAT DOES BLOOD TYPE SIGNIFY, AND HOW DOES IT DIFFER FROM OTHER BLOOD TYPES?

The letters A, B, and O stand for different variants of the ABO gene, which program human blood cells to produce different blood groups in different ways. Your body is built to create A and B antigens on red blood cells if you have type AB blood, for example. Antigens are not produced by people with type O blood.

The presence of proteins on red blood cells determines whether blood is “positive” or “negative.” Rh-positive means your blood contains proteins.

People with type O- blood are referred to as “universal donors” since their blood has no antigens or proteins, allowing it to be accepted by anybody in an emergency.

But then why do distinct blood types exist? Experts believe that variables such as where someone’s ancestors came from and previous infections that resulted in defensive changes in the blood may have led to the variety. People with type O blood are more likely to get sick from cholera, while those with type A or B blood are more likely to have blood coagulation problems. Although our blood can’t keep up with the various biological or viral hazards that circulate in real-time, it may represent what has occurred previously.

The blood types most at-risk for heart disease

According to the American Heart Association, those with type A, type B, or type AB blood are more likely than people with type O blood to suffer a heart attack or develop heart failure.

Whereas the risk of heart attack and heart failure is minor (types A and B had a combined 8% greater risk of heart attack and 10% higher risk of heart failure in one big research), the variation in blood clotting rates is significantly higher, according to the AHA. People with type A and B blood were 51 percent and 47 percent more likely, respectively, to develop deep vein thrombosis and pulmonary embolism, both of which are serious blood clotting diseases that can increase the risk of heart failure.

Many scientists believe that inflammation in the bodies of persons with type A, type B, or type AB blood could be one cause of this elevated risk. Type A and type B blood proteins may create more “blockage” or “thickening” in the veins and arteries, increasing the risk of clotting and heart disease.

Experts believe this could also explain the anecdotal (but inconclusive) reduction in the risk of serious COVID-19 disease in people with type O blood, which has prompted an investigation. Heart difficulties, blood clotting, and other cardiovascular disorders are common with severe COVID-19 disease.

Other consequences of blood type

People with type O blood have a lower risk of heart disease and blood clotting, but they are more likely to experience hemorrhaging or bleeding disorders. According to a study on postpartum blood loss, which indicated an elevated risk in women with type O blood, this may be especially true after childbirth.

According to a study published in Critical Care, those with type O blood may fare worse after a catastrophic injury due to higher blood loss.

Other studies have discovered that people with type AB blood had a higher risk of cognitive impairment than people with type O blood. Memory, concentration, and decision-making problems are all examples of cognitive impairment.

SHOULD I CHANGE MY LIFESTYLE BASED ON MY BLOOD TYPE?

While a recent study suggests that blood type can influence a person’s chance of getting heart disease, other important factors such as nutrition, exercise, and even the degree of pollution in your neighborhood all play a role in heart health.

Experts feel that regardless of a person’s blood type, they would make no additional recommendations for patients attempting to maintain their heart-healthy other than a good heart-healthy diet that minimizes inflammation.

Future studies, however, experts believe, could provide more definitive ways for doctors to treat patients depending on their blood type. Taking aspirin every day may benefit a patient with healthy cholesterol levels and type A blood, but it may not be necessary for a patient with type O blood.