Cardiovascular disease and ABO blood-groups in Africans. Are blood-group A individuals at higher risk of ischemic disease?: A pilot study

Background: Since the discovery of the ABO blood group system by Karl Landsteiner in 1901, several reports have suggested an important involvement of the ABO blood group system in the susceptibility to thrombosis. Assessing that non-O blood groups in particular A blood group confer a higher risk of venous and arterial thrombosis than group O. Epidemiologic data are typically not available for all racial and ethnics groups. The purpose of this pilot study was to identify a link between ABO blood group and ischemic disease (ID) in Africans, and to analyze whether A blood group individuals were at higher risk of ischemic disease or not. Methods: A total of 299 medical records of patients over a three-year period admitted to the cardiology and internal medicine department of military hospital of Ouakam in Senegal were reviewed. We studied data on age, gender, past history of hypertension, diabetes, smoking, sedentarism, obesity, hyperlipidemia, use of estrogen-progestin contraceptives and blood group distribution. In each blood group type, we evaluated the prevalence of ischemic and non-ischemic cardiovascular disease. The medical records were then stratified into two categories to evaluate incidence of ischemic disease: Group 1: Patients carrying blood-group A and Group 2: Patients carrying blood group non-A (O, AB and B). Results: Of the 299 patients whose medical records were reviewed, 92 (30.8%) were carrying blood group A, 175 (58.5%) had blood group O, 13 (4.3%) had blood group B, and 19 (6.4%) had blood group AB. The diagnosis of ischemic disease (ID) was higher in patients with blood group A (61.2%) than in other blood groups, and the diagnosis of non-ischemic disease (NID) was higher in patients with blood group O (73.6%) compared to other groups. In patients with blood group B or AB compared to non-B or non-AB, respectively there was no statistically significant difference in ID incidence. Main risk factor for ID was smoking (56.5%), hypertension (18.4%) and diabetes (14.3%). In our study, there was no statistical difference between blood group A and non-A in myocardial infarction (MI) incidence (p = 0.09, 95% CI = 0.99–2.83) but a statistically significant difference between blood group A and non-A in stroke and coronary artery disease (CAD) incidence (p < 0.0001, 95% CI = 1.80–3.37 and p < 0.0001 95% CI = 1.82–3.41 respectively) was found. The incidence of ID in men was significantly higher in blood group A (95% CI = 2.26–4.57, p < 0.0001) compared with non-A group, while there was no statistically significant difference in women (p = 0.35). However, an overall effect was detected to be statistically significant regardless of gender (p < 0.0001). Conclusion: Our study suggests an association between blood group A and ID in sub-Sahara Africans. In African countries, where most of health facilities are understaffed, more rigorous studies with a larger population are needed to give a high level of evidence to confirm this association in order to establish the need to be more aggressive in risk factor control in these individuals