In one study that found such an association, the researchers note there was also a higher number of diabetes cases among individuals with blood type AB. Other studies - although small - have reported similar findings. This led them to investigate the link between blood type and diabetes in a larger cohort.
Dr. Fagherazzi and colleagues analyzed data from 82,104 women who were a part of the French E3N study - a cohort of almost 100,000 female teachers that began in 1990.
From an analysis of health questionnaires the women completed, the team identified 3,553 women who received a diagnosis of type 2 diabetes between 1990 and 2008. Blood samples from the women were collected between 1995 and 1997.
Women with blood type B+ at 35% higher risk of type 2 diabetes. The results of the analysis revealed that women with blood type A were 10% more likely to develop type 2 diabetes than women with blood type O, while women with blood type B were 21% more likely to develop the condition.
Women with blood type AB were found to be at 17% higher risk of type 2 diabetes than those with blood group O, but the researchers say this result was "not statistically significant."
The team then assessed the women's risk of diabetes by their Rhesus factor - the presence of Rhesus antigens in the blood. However, they found there was no difference in type 2 diabetes risk between those who were Rhesus positive (R+) and those who were Rhesus negative (R-).
Next, the team assessed the risk of type 2 diabetes by both women's blood type (A, B, AB or O) and Rhesus factor. Each possible combination was compared with blood group O negative (O-), as this is classed as a universal blood group because it has no A, B or Rhesus antigens present.
The researchers found that women who were blood group B positive (B+) were 35% more likely to develop type 2 diabetes than those with blood group O-. Women with blood group AB+ were at 26% higher risk of type 2 diabetes, those with blood group A- were at 22% higher risk and those with blood group A+ were at 17% increased risk.
The team says their findings for blood groups O-, B- and AB- were not statistically significant.
Commenting on their results, Dr. Fagherazzi says:
"Our findings support a strong relationship between blood group and diabetes risk, with participants with the O blood type having a lower risk of developing type 2 diabetes.
Therefore, the effects of blood groups should be investigated in future clinical and epidemiological studies on diabetes. Further pathophysiological research is also needed to determine why the individuals with blood type O have a lower risk of type 2 diabetes."
However, the team suggests a number of potential factors that might explain their findings. For example, they point out that blood grouping is linked to specific molecules related to type 2 diabetes. Another study has associated blood type with gut bacteria composition, which may be linked to type 2 diabetes.
Study author Dr. Françoise Clavel-Chapelon - also of the Center for Research in Epidemiology and Population Health at the Gustave Roussy Institute - acknowledges the fact that their study population only included women but notes that no biological mechanisms were identified that suggest their findings were sex-dependent.
"Information on the participants was self-reported, but this is unlikely to substantially affect the results," he adds.