The association between blood group and the risk of vascular disease in Quebec blood donors

Background. The association between antigens A and B and arterial thrombosis, such as coronary heart disease, cerebrovascular disease or peripheral vascular disease, is still unclear. We evaluated the association between blood groups and thrombotic events in a cohort of blood donors from the province of Quebec, Canada. Material and methods. Among all whole blood donors aged >= 18 years in Quebec between June 1990 and March 2009, a study sample with known blood groups was linked with the provincial hospitalisation and death records to count vascular events. All hospital admissions and deaths with codes for primary and relevant secondary diagnoses of coronary, cerebrovascular or peripheral diseases, including coronary heart disease interventions, were included. Cox regression was used to evaluate the hazard ratio associated between blood groups and these events adjusted for other baseline characteristics. Results. Among the blood donors, 64,686 had a known blood group and were linked with the provincial health databases. The mean age of these donors was 38 years. The Cox multivariate adjusted hazard ratio for coronary, cerebrovascular or peripheral diseases was 1.19 (95% confidence interval: 1.01-1.40) for subjects with blood group AB compared to those with blood group O. There were no statistically significant associations with other blood groups. Only among women aged >= 40 years did those with blood group A have a higher hazard ratio for coronary heart disease (1.40 [1.01-1.92]) than those with blood group O, after adjusting for other characteristics. Discussion. When compared to blood group O, only blood group AB was associated with a higher risk of hospitalisation or death because of thrombotic events such as coronary, cerebrovascular or peripheral diseases. However, the associations differed according to age and sex because only females aged >= 40 years with blood group A had a higher risk of coronary heart disease.