ABO Blood Type Is a Risk Factor for Coronary Heart Disease

August 15, 2012

August 14, 2012 (Boston, Massachusetts) — Data from two prospective cohort studies have identified the ABO blood group as a risk factor for the development of coronary heart disease [1]. Individuals with blood groups A, B, or AB were 5% to 23% more likely to develop coronary heart disease compared with subjects with O blood type, and the associations were not altered by multivariate adjustment of other risk or dietary factors.

The analysis, led by Dr Meian He (Harvard School of Public Health, Boston, MA), included 62 073 women from the Nurses' Health Study (NHS) and 27 428 men from the Health Professionals Follow-up Study (HPFS) and is published in the September 2012 issue of Arteriosclerosis, Thrombosis, and Vascular Biology.

In the NHS and HPFS, the incident rates of coronary heart disease per 100 000 person-years were 125, 128, 142, and 161 for women with type O, A, B, and AB, respectively, and 373, 382, 387, and 524 for men with type O, A, B, and AB, respectively. Compared with individuals with O blood type, individuals with blood group A, B, or AB had a respective 5%, 11%, and 23% increased risk of developing coronary heart disease in an age-adjusted model. These associations were not significantly altered in the multivariable-adjusted risk model.

Age-Adjusted Hazard Ratios (95% CI) for Coronary Disease by ABO Blood Type

Cohort Blood group O Blood group A Blood group B Blood group AB
NHS 1.0 1.04 (0.94–1.15) 1.14 (1.00–1.30) 1.20 (1.02–1.40)
HPFS 1.0 1.07 (0.96–1.18) 1.10 (0.95–1.27) 1.26 (1.07–1.48)
Combined NHS and HPFS 1.0 1.05 (0.98–1.13) 1.11 (1.01–1.23) 1.23 (1.10–1.37)

The researchers also performed an analysis examining the risk of coronary heart disease in patients with non-O blood type. Compared with individuals with O blood type, those with A, B, and AB had a 9% increased risk of developing coronary heart disease, and this risk was unaltered after adjustment for other risk factors. Similarly, a combined analysis of NHS and HPFS with four other prospective studies, an analysis that included 114 648 subjects, found there was a 6% increased risk of coronary heart disease for those with non-O blood type compared with individuals with O blood.

In total, just over 6% of the coronary heart disease cases were attributable to the A, B, or AB blood types, according to the researchers.

In terms of possible underlying mechanisms for the increased risk, He et al note that in non-O individuals, plasma levels of factor VIII-von Willebrand factor (vWF) are approximately 25% higher than in individuals with type O blood type. Elevated levels of factor VIII-vWF have been previously identified as a risk factor for coronary heart disease.

"The vWF has an important role in hemostasis and thrombosis by mediating platelet adhesion to the vascular wall, especially under high shear stress conditions," explain He and colleagues. "Along with fibrinogen, vWF also participates in platelet aggregation and plays a role in the development of atherosclerosis." In addition, the A blood group has been shown to have higher levels of total and LDL cholesterol.

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