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VERIFIED CONTENTAuthor: Karolina Karabin, MD, PhD, molecular biologist, laboratory diagnostician, nutrition and lifestyle consultant

Information about blood groups is primarily used in transfusion medicine because it is very dangerous to transfuse blood with the wrong group. However, research shows that the role of blood groups in medicine is much broader and that they can also reduce or increase the risk of certain diseases.

Depending on the set of molecules on our blood cells (antigens), blood can be classified as group A, B, AB or 0. This is the most important division into blood groups called AB0, but there are also other group systems, e.g. Rh, Kell, Duffy.

AB0 blood groups result from the presence of molecules called polysaccharides on the surface of blood cells, which differ slightly in structure. It turns out that the presence or absence of these polysaccharides is not only limited to the surface of blood cells, and is ubiquitous in other body fluids and tissues. This, in turn, translates into changes in the structure of cells, both in terms of their structure and function.

Blood group and diseases

The molecules that determine blood groups have many functions. They can act as attachment sites for viruses, bacteria and parasites, transport nutrients into the cell, or metabolize chemicals as enzymes. As a result, their role goes far beyond information in the context of blood transfusions or donations at blood donation centers, and research shows that they have the potential to influence the risk of certain diseases.

As early as the 1960s, large-scale epidemiological studies investigating the relationship between AB0 blood groups and susceptibility to disease were conducted all over the world. However, it is worth emphasizing that so far in many cases the mechanism of this relationship has not been explained and in many cases it requires further research.

Current research indicates that certain blood groups may be associated with risk:

  • sickle cell anemia,
  • of hemolytic disease of newborns,
  • thromboembolism,
  • ischemic stroke,
  • myocardial infarction,
  • hypertension,
  • type 1 diabetes and type 2 diabetes,
  • dementia and disorderscognitive functions,
  • bacterial diseases, e.g. plague, cholera, tuberculosis,
  • viral diseases, e.g. mumps, smallpox, "stomach flu",
  • parasitic diseases, e.g. malaria,
  • gastric and duodenal ulcers,
  • cancers, e.g. leukemias, lymphomas, stomach cancer.

Blood group - cardiovascular diseases

The most consistent studies examining the association of AB0 blood groups with diseases concern the risk of venous thromboembolism. Venous thromboembolism causes blood clots to form in deep veins, e.g. in the extremities.

It has been shown that people with blood group A, B or AB are more likely to develop thromboembolism than people with blood group 0. This is probably due to the association of particular blood groups with the concentration of blood coagulation factors.

People with blood group 0 have about 25% lower concentration of von Willebrand factor (vWF) and factor VIII compared to people with blood groups A, B or AB, which partially protects them against thromboembolism. However, on the other hand, they make people with blood type 0 more prone to bleeding because their blood is harder to clot.

In other studies, people with blood groups A, B, or AB have been found to have a higher risk of coronary heart and peripheral vascular disease, myocardial infarction, and angina. These observations have also been confirmed in genome wide association studies (GWAS) and in a systematic review and meta-analysis of the data.

It has been shown that the variants of genes encoding blood groups A, B and AB, compared to group 0, are associated with an increased concentration of lipids and inflammatory markers, e.g. tumor necrosis factor alpha in the blood. These markers are well known factors that increase the risk of the previously mentioned diseases.

Blood group - dementia and cognitive impairment

Higher levels of blood clotting factors in people with blood groups A, B, or AB, in addition to their impact on the risk of cardiovascular disease, may also be associated with an increased risk of dementia and cognitive impairment.

In large prospective case-control studies it has been shown that people with these blood groups are up to 82% more likely to develop dementia and cognitive disorders compared to people with blood group 0. Importantly, the risk was independent of the region geography, age, race and gender.

Blood group - cancer

It has been shown that people with blood group A, compared to people with blood group 0, show a higher incidence of:

  • salivary gland cancer (64%),
  • stomach cancer (22%),
  • ovarian cancer (28%),
  • canceruterus (15%),
  • cervical cancer (13%),
  • colorectal cancer (11%).

Scientists speculate that this may be due to the difficult elimination of cancer cells in people with blood group A compared to people with blood group 0. It turns out that some people with blood group 0 can develop neoplasms on the surface of which they are located same or similar molecules to people with blood group A.

Such molecules can then be recognized as foreign and contribute to the elimination of neoplastic cells in people with group 0. However, in people with blood group A, cancer cells with such particles may be invisible to the immune system due to the similarity to their own tissues .

Remember, however, that neoplasms are multifactorial diseases and although their risk is correlated with the presence of certain blood groups, it does not mean that they cause neoplasms. Conversely, the lack of correlation does not mean that we will not get sick.

Blood group - infectious diseases

The same molecules on the surface of blood cells can also be found on epithelial cells in the digestive tract or the respiratory tract. For this reason, they are used as receptors through which parasites, bacteria and viruses enter our body.

It has been shown that people with blood group 0 are more susceptible to gastric and duodenal ulcers compared to people with blood groups A, B or AB, and as it is known, one of the causes of their formation is chronic Helicobacter pylori infection.

Increased risk of ulcers in people with blood group 0 is explained by the fact that the attachment of Helicobacter pylori to the gastric mucosa is mediated, among others, by Lewis b protein, which may inhibit the binding of bacteria.

This may explain the reduced number of infections in people with blood groups A, B, or AB compared to people with blood group 0. Although recent studies have shown that this association may also be dependent on the Helicobacter pylori strain.

Another example of susceptibility to infections associated with blood groups are viral infections caused by Noroviruses, which are the most common cause of the so-called stomach flu. It has been shown that people with blood type 0 may be more susceptible to infection by Noroviruses, and people with blood type B less.

In addition, blood group 0 has been shown to be able to protect against malaria in some way. The malarial parent is a parasite of red blood cells that forms the so-called rosettes with uninfected blood cells. They can then adhere to the endothelium of the vessels, causing them to close and cause disease symptoms. One study showed that people with blood group 0 compared to otherswith blood groups, they form a smaller number of rosettes.

Blood group - hemolytic disease of newborns

Blood group may also contribute to the development of haemolytic disease of newborns, which is most often associated with the RhD blood group system. The disease occurs when the child's parents differ in blood groups in the Rh system and it is called serological conflict.

Conflict occurs when the RhD mother is negative (RhD-) and the baby is positive (RhD +). The consequence is the production of IgG antibodies by the mother against the fetal red blood cells, causing them to break down.

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