ABO Blood Group - A Cardiovascular Connection
By Shashi Agarwal MDCardiovascular disease is now the number one killer in the world. Although the major risk factors such as hypertension, diabetes mellitus, hypercholesterolemia, obesity, physical inactivity and smoking are well known, some minor risk factors remain relatively unknown. The ABO blood group is one such minor risk factor.
Austrian scientist, Karl Landsteiner earned a Nobel Prize for the discovery of the ABO blood group system in 1901. Inherited antigenic substances on the surface of the red blood cells allow a classification of the blood into different groups (blood type). Lawyers soon started using this in paternity suits, police in forensic science and anthropologists in the study of different populations. The Japanese, started believing that a person's blood type is predictive of their personality, character, and compatibility with others. Its major impact however, was in preventing fatal reactions to blood transfusions.
If transfusion is given without proper typing and cross-matching, naturally occurring antibodies in the recipients blood can bind to corresponding antigens on the transfused red blood cells resulting in an acute hemolytic transfusion reaction that can cause widespread intravascular blood clotting, shock, acute renal failure, and death.
Another major health impact was understanding the patho-physiology behind the hemolytic disease of the newborn. This dangerous reaction occurs as the anti A and anti B antibodies produced in the O blood mother cross the placenta and enter the blood stream of her infant with type A or type B blood. However, due to lower number of fetal antigens, the reactions are usually less severe.
Recent reports have noticed an interesting connection of these blood types with cardiovascular disease. In a presentation at the Annual Scientific Meetings of the American Heart Association in November 2011, researchers from the Harvard School of Public Health reported that men and women in the AB blood group had a 26% higher risk of developing stroke when compared with those with type O blood. Women with type B had a 15% higher risk of stroke, when compared with those with type O blood. They analyzed data from two major studies - the Nurses' Health Study (NHS) which included 61,973 women and the Health Professionals Follow-up Study (HPFS) which included 27,808 men. The follow up was 26 years and 20 years.
In a study published in the New England Journal of Medicine in the December 9, 1971 issue, researchers investigating 10,000 Israeli male government employees 40 years of age and over as part of the Israeli Ischemic Heart Disease Project (five year duration) found that subjects with blood Groups A, B, and AB tended to have higher incidence rates of myocardial infarction than those with other blood groups. High rates were also noted in A and B subjects for angina pectoris. Subjects in blood Group O tended to have lower rates of infarction and angina pectoris than those of other groups.
Researchers reported a higher incidence of elevated cholesterol levels and ischemic heart disease in non-O group individuals in the British Medical Journal in June 1990. The results emanated from a prospective study of 7662 men with known blood groups. Many other studies have similarly found increased heart attacks in non-O blood group individuals.
In another study published in the February 2009 issue of the Journal of Thrombosis and Haemostasis, researchers reported a higher tendency for arterial and venous clotting in patients with non-O blood groups. Several studies have demonstrated the influence of the ABO blood group on plasma levels of von Willebrand factor. VWF is major player in blood clotting.
In summary, non-O blood group individuals suffer a higher risk of myocardial infarction, angina, cerebral strokes and venous thrombo-embolism than those with group O blood. This increased risk, although real, is not very significant. Since your blood group cannot be changed, non-O blood group people should follow heart healthy lifestyles more judiciously, to nullify any increased genetic risk conferred by their blood type.
Dr. Shashi K. Agarwal is a Board Certified Internist and Cardiologist with a private practice in New York City and New Jersey. He is also a diplomate of the American Board of Holistic Medicine and the American Academy of Anti-Aging Medicine.
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