Blood groups and diseases: Written in your blood

There are people who tell you about their Blood type as if it were their zodiac sign, so much so that many believe it defines them as people. Few know that groups A, B, AB and 0 (what is known as the AB0 system) are a consequence of human evolution and that each letter refers to the presence or absence of antigens (substances that can provoke immune responses) on the surface of red blood cells. Thus, group A has A antigens; group B, antigens B; the BA possesses both antigens; and the 0 has none.

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And how common are these groups? Worldwide, the most abundant group is 0+ (36.45%); they are followed by A + (28.3%), B + (20.6%) and AB + (5%). Then come the 0- (4.3%), the A- (3.5%), the B- (1.4%) and the AB- (0.45%). In Spain, according to the National Federation of Blood Donors, we comply, more or less, with those proportions. The most abundant group is 0+ (36%), followed by A + (34%). But we have some peculiarities. As in most European countries, group B + is less frequent than the world average. Instead, the frequency of negative RH in Spain is double that in the rest of the world. And all this has repercussions on our health. Do you want to know which ones? Well keep reading.

The health that runs through your veins

Recent studies published in prestigious scientific journals have established the relationship between different blood groups and the risk of developing chronic diseases. This is what they have seen:

  • Cancer. A 2015 study of more than 50,000 people between the ages of 40 and 70 (published in BMC Medicine) found that people with groups A, B, or AB had a higher risk of stomach cancer than those in group 0. Although the Blood group did not appear to influence overall cancer mortality, another review of studies (published last year in Future Science OA) did link group 0 to a lower risk of various malignant tumors, including those of the stomach, pancreas and colon. For its part, the American Cancer Society includes blood type A among risk factors for stomach cancer.
  • Cardiovascular disease. A 2012 study evaluated 20 years of data corresponding to 62,000 women included in the prestigious Nurses' Health Study, and 27,000 men included in the Health Professionals Follow-up Study. Conclusion? The experts found that people with blood group AB had a 23% higher risk of developing cardiovascular disease than those in group 0; those of group B, 11% more risk than these; and those of group A, a 5% higher risk.
  • Type 2 diabetes. French researchers studied the health data of more than 82,000 women and found that those with blood groups A and B also had a higher risk of type 2 diabetes than those of group 0. The study was published in Diabetologia.
  • Malaria. Again, people with blood group 0 are more protected against the most dangerous form of malaria (caused by the Plasmodium falciparum parasite and transmitted by mosquitoes). Swedish researchers verified how a protein secreted by this parasite adheres more strongly to type A red blood cells than to type 0, thus increasing the risk of developing the disease. The work was published in 2015 in Nature Medicine.

Conclusions

Although studies link blood group 0 with fewer health risks, researchers insist that it is not possible to speak of cause / effect nor does it mean that a specific blood group will generate a certain disease. Instead, the data can encourage us to adopt a healthy lifestyle (with regular exercise, enough rest, a diet rich in fresh products and poor in processed products, outdoor life and anti-stress methods), which has been shown to reduce risk of lots of chronic diseases.

RH NEGATIVE AND PREGNANCY

  • RH factor is a protein found on the surface of red blood cells. If you do, you are HR positive; if not, you are HR negative. Do not worry if your RH is negative, because it does not influence health risks, except if you are pregnant. If your baby is RH positive and you are RH negative, your body can produce RH antibodies when exposed to their blood. These antibodies are not usually a problem in the first pregnancy, but they are in subsequent ones. If your second baby (and those that follow) is RH positive, your body will produce antibodies capable of causing severe anemia. Specific tests allow today to assess this risk and take preventive measures in time.

When transfusions were dangerous

  • Before blood groups were discovered, transfusions could have fatal consequences. In the case of blood group, if a person with group A blood receives group B blood, the immune antibodies will respond by attacking the B antigens, and the red blood cells will clump together and block the blood vessels in vital organs. Although the AB0 system remains the most important, the International Transfusion Society recently recognized 33 different blood group systems, corresponding to 300 antigens. In fact, today groups other than the AB0 system are determined before a transfusion.

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