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.
AB blood type and an 82% higher risk of dementia-related memory loss
The AB blood type is the rarest in the United States, accounting for roughly 4% of the American population. It is also the group most associated with cognitive decline in later life, according to one study cited in the source material.
Researchers found that individuals with AB blood were 82% more likely to develop memory and cognitive issues linked to dementia than people with any other blood type. The study does not identify a confirmed biological mechanism, but the statistical gap between AB and other groups is described as substantial.
