Non-O Blood Types May Impart Higher Cardiovascular Risk

Confirming results from smaller studies, a meta-analysis shows that people with non-O blood types have slightly elevated risks of coronary and combined cardiovascular events.

Non-O blood types conferred relative 9% greater risks of both endpoints, although the absolute differences were small: 1.5% versus 1.4% for all coronary events and 2.5% versus 2.3% for combined cardiovascular events, master’s degree student Tessa Kole (University Medical Center Groningen, the Netherlands), reported on April 30 during a poster presentation at Heart Failure 2017 in Paris, France.

“After further assessment of this phenomenon, it could be included in therapy algorithms, leading to a lower threshold for treatment in non-O subjects,” her poster reads.

Mary Cushman, MD (University of Vermont Medical Center, Burlington), who was not involved in the analysis, told TCTMD that even though the findings are consistent with prior observational studies, it would be premature to incorporate them into clinical decision-making, saying that “there’s a lot more to learn.”

In particular, the mechanisms underlying the link between blood type and risk as well as clarity on whether there are any interventions that alleviate the elevated risk in people with non-O blood types need to be studied further, she said.

This is a good topic for clinicians to know about, Cushman said, “but I don’t think they should be going out and measuring blood type in everybody if they don’t already have that information, because we’re not really sure what to do about it.”

For the meta-analysis, Kole and colleagues pooled data from 11 prospective cohort studies that included a total 1,362,569 participants. Those with non-O blood types were more likely to have a coronary or cardiovascular event, but the odds of a fatal coronary event did not differ between groups (OR 1.00; 95% CI 0.85-1.18).

Exclusion of the largest cohort study—which accounted for 53% to 56% of the weight in the analyses—yielded similar results, although the relationship between non-O blood type and combined cardiovascular events was no longer significant. 

Cushman said the purported mechanism behind the observed relationships involves glycosylation of Von Willebrand factor. The enzymes responsible for the process make it so the procoagulant protein is cleared more slowly in patients with non-O blood types. That results in higher concentrations, increasing risks of thrombosis and vascular problems. 

But it’s possible that other proteins are involved, as well, and the potential mechanisms require further study, Cushman said.