The 2024 review examined 51 systematic reviews with meta-analyses covering 270 reported associations between ABO and Rhesus (Rh) blood groups and different health outcomes.
Researchers found that the association between blood group B and type 2 diabetes was the only one among the 270 links to meet the highest standard of evidence.
The study was led by epidemiologist Fang-Hua Liu of Shengjing Hospital of China Medical University and colleagues.
Blood groups are determined by antigens on the surfaces of red blood cells. The ABO system classifies blood as A, B, AB or O, while the Rhesus factor determines whether it is positive or negative.
Previous studies have investigated whether these differences are associated with susceptibility to various diseases, but their findings have often been inconsistent.
To assess the evidence, Liu and colleagues searched scientific databases, including PubMed, Web of Science, Embase and the Cochrane Library, for systematic reviews and meta-analyses of observational studies published up to February 16, 2024.
They examined the strength and consistency of the findings, the size of the datasets and potential biases that could affect the results.
Most of the reported associations did not meet the required standards. Only the link between blood group B and type 2 diabetes was supported by convincing evidence.
However, the review did not establish why people with blood group B might face a higher risk.
The reported 28 per cent increase represents a relative increase in risk, not a 28-percentage-point rise in an individual’s absolute likelihood of developing diabetes.
Established risk factors, including excess body weight, physical inactivity and unhealthy dietary habits, remain important considerations in type 2 diabetes prevention.
The researchers did not investigate the biological mechanisms that might explain the blood group association. Other research has suggested a possible role for the gut microbiome, but further investigation is needed.
The findings do not mean that everyone with blood group B will develop diabetes or that people with other blood groups are protected from the condition.
Rather, the review identifies a potential risk association that warrants further research. Scientists will need to determine whether blood group information can improve diabetes risk assessments when considered alongside established clinical and lifestyle factors.
