People with the AB blood group are more likely to develop memory problems than those with other blood groups, according to scientists in the United States.
The study is part of a larger investigation by experts at the University of Vermont School of Medicine, who analyzed data from 30,000 citizens over the age of 45.
From this initial group, the researchers identified 495 participants who had developed memory or cognitive problems during a three-year monitoring period. And these participants were in turn compared to tests of more than 500 people without cognitive problems.
The researchers found that people with type AB are 82% more likely to have memory and attention problems than those of other blood groups.
These types of problems could be indicative in some cases of a future development of dementia, but the scientists clarified that the study stopped short of determining the links between blood groups and that disease.
diet and exercise
Other previous studies had already shown that people in group O have a lower risk of cardiovascular disease and stroke.
«Our blood study focuses on the type and risk of cognitive problems, but other studies have already shown that factors such as high blood pressure, high cholesterol and diabetes increase the risk of cognitive difficulties and dementia,» said Mary Cushman, who led the investigation.
«Our work shows even more clearly the connections between vascular problems and the brain.»
However, the study results cannot be applied to dementia, a disease more complex than the memory problems being monitored by scientists in Vermont.
Therefore, it could not be said that the AB group would generate an increased risk of dementia, said Simon Ridley, head of research at Alzheimer’s research in the UK.
«From what we know so far, the best way to maintain a healthy brain is to eat a balanced diet, not smoke and exercise regularly,» Ridley told the BBC.
More than a century after the discovery of blood groups, why they exist and how they determine a higher or lower risk of developing certain diseases remains largely a mystery.
It was in 1900 that the Austrian biologist and pathologist Karl Landsteiner discovered blood groups, which earned him the Nobel Prize in Medicine in 1930.
Landsteiner analyzed the blood of members of his laboratory, including his own, and separated in each case the red blood cells and the serum, the fluid that remains when the red blood cells are removed, and the clotting factor.
The scientist then combined the serum of one person with the red blood cells of another and vice versa and showed that in some cases the red blood cells clumped together forming clumps.
Landsteiner thus classified three groups that gave rise to different reactions, which he arbitrarily called A, B, and C. This last group was renamed O. Shortly after, two of his disciples matched a fourth group, AB.
In the middle of the 20th century, an American scientist, Philip Levine, discovered another type of categorizing blood, according to the presence of the Rh blood factor. A plus or minus symbol next to the group letter indicates whether the factor is present. This hot (substance that generates an immune response) was called Rh because it was found in the serum of rabbits immunized with the blood of an Indian monkey, the Rhesus macaque.
The discovery of blood types was vital for transfusions, since not all blood types are compatible, and clumping of red blood cells can block circulation and be fatal to the patient.