Most people never think about their blood type beyond an emergency room visit — but research suggests it may be a meaningful indicator of health risks across a lifetime. Studies have linked the ABO blood group system to varying susceptibility to heart disease, cognitive decline, gastric cancer, and ulcers. Here is what the science currently documents for each blood type.
In brief
- —AB blood type is the rarest, affecting around 4% of Americans
- —A and B types carry a 51% higher deep vein thrombosis risk
- —Type O blood is not risk-free — ulcers are more prevalent
How the ABO system classifies blood — and why a mismatch can be fatal
The ABO blood group system, developed by Dr. Karl Landsteiner, categorizes blood into four types — A, B, AB, and O — based on proteins called antigens present in red blood cells and plasma antibodies. A second layer of classification comes from the Rh factor: if the Rh antigen is present, blood is Rh positive; if absent, it is Rh negative.
This classification is critical in medical settings, particularly for blood transfusions. According to Dr. Guggenheim of the Abramson Cancer Center Cherry Hill, "When antigens come into contact with substances that are unfamiliar to your body, such as certain bacteria, they trigger a response from your immune system. The same type of response can occur during a blood transfusion if your donor’s blood type doesn’t match with yours. In that case, your blood cells could clump and cause potentially fatal complications."
Testing for blood type involves mixing a blood sample with antibodies against type A and B blood, then observing whether the cells clump. A secondary test mixes the liquid part of blood with type A and B samples. Type A blood contains anti-B antibodies; type B contains anti-A antibodies; type O contains both, which is why it can be donated to individuals of any blood type.
A classification system over a century old
The ABO blood group system was established by Dr. Karl Landsteiner in the early 20th century and remains the standard framework for blood classification in medicine today. Blood type is inherited genetically and determined by the presence of specific antigens on red blood cells, as well as the Rh factor. While blood typing is routinely used in transfusion medicine, its implications for long-term disease risk have become an active area of epidemiological research.
A and B blood types linked to 8% higher heart attack risk and 51% more deep vein thrombosis
People with type A or type B blood face a measurably higher risk of cardiovascular events, according to a study published in the American Heart Association journal. Researchers found that individuals in these groups had a combined 8% greater risk of heart attack and a 10% greater risk of heart failure compared to those with other blood types.
The same study found that A and B blood type individuals had a 51% greater chance of developing deep vein thrombosis — a blood clot that typically forms in the legs — and a 47% higher risk of pulmonary embolism, a potentially life-threatening blockage in the lungs.
These findings do not establish direct causation, but they indicate a statistically significant association between blood type and cardiovascular vulnerability that researchers say warrants attention in clinical risk assessments.
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