Previous studies have found that people with blood type A or B were more likely to have cardiovascular disease or experience a blood clot than people with type O blood, and that people with type O blood were more likely to have a bleeding condition. One of the first such studies was published in 1962, demonstrating a relation between the ABO system and ischemic heart disease. Others have suggested that people with certain blood types may be more susceptible to some infectious diseases. Other prominent examples include associations with risks of a number of infectious diseases, to the extent that the allele distribution of the blood group antigens has evolved to reflect some areas endemic to these infectious diseases. This is in part true for infectious disease such as Plasmodium falciparum malaria, Helicobacter pylori and Vibrio cholerae, where ABO blood groups are involved in different aspects of pathogenesis, from microbe attachment and entry into cells to subsequent disease development and severity of disease.
Now a team of scientists from the Karolinska Institutet, Sweden, suggests in a study published in eLife, that people with certain blood types are more likely to have blood clots or bleeding conditions, kidney stones, or pregnancy-induced hypertension, The study confirms previously identified connections between certain blood types and the risk of blood clots and bleeding, and makes a new connection between kidney stones and having type B blood as compared to O. The discoveries may lead to new insights on how a person’s blood type may predispose them to developing a certain disease. Using the Scandinavian Donation and Transfusion (SCANDAT) database, the team has previously studied associations between ABO blood groups and cancer subtypes, cardiovascular and thromboembolic disease, the occurrence of dementia and degradation of bioprosthetic aortic valves in relation to ABO blood group.
The RhD antigen, on the other hand, has a less clear link to health outcomes. RhD status has mainly been linked to alloimmunization of the pregnant women with hemolytic disease of the fetus and newborn (HDFN) as a consequence. Also there is still very little information available about whether people with RhD-positive or RhD-negative blood groups may be at risk of certain diseases, or how many more diseases may be affected by blood type or group. In this large cohort study of 5.1 million unique persons followed over 70 million person-years, scientists performed an agnostic analysis of associations between the ABO and RhD blood groups and the risk of 1,217 distinct disease categories. After multiple testing adjustment and comparison with a validation cohort, 49 and 1 associations between disease categories and blood group for ABO and RhD remained significant, respectively.
Their findings confirmed that people with type A blood were more likely to experience a blood clot and that those with type O blood were more likely to experience a bleeding disorder. They also verified that women with type O blood or RhD-positive were more likely to experience pregnancy-induced hypertension. Thyrotoxicosis was also less common in blood group A and AB as compared to blood group O. Pancreatic cancer was the only malignancy that remained associated with a blood group, specifically blood group A as compared to O. A new finding was that of kidney and ureter stones, which were found to be less common in blood group B as compared to O. Cholelithiasis, which has been disputed, was more common in blood group A and AB as compared to blood group O. Be as it may, most of the investigated disease or disease groups, however, do not seem to be strongly influenced by the ABO blood group of the individual.
As to possible mechanisms explaining the associations identified, the team may only speculate hypotheses to be further tested. It is however peculiar to identify a condition, such as renal caliculi, with highly variable distribution, in regard to geographic region, to have an association to blood group. A possible mechanism could be, when considering the full spectrum of disease categories investigated, that lower urine pH in diabetic patients, a disease category also associated with an increased incidence in blood group B, may result in stone formation. A limitation of the study that prevents strong casual inference is the possibility some of the observed associations between ABO blood group and disease categories were driven by other disease associations with ABO blood group. This might, for example, be the case for the associations between blood group A and diabetes as well as hyperlipidemia, which are potentially driven not by a causal association but possibly instead by an association between blood group A and ischemic heart disease, at the occurrence of which diabetes and lipid disorders are screened for and thus frequently diagnosed.
The authors say that more studies are needed to confirm the results and to determine how different blood types or groups may increase the risk of certain diseases, or whether there are alternative explanations for these relationships.
- Edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
Dahlén T et al. eLife 2021 Apr 27 (online); 10:e65658.
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