Gender difference in rheologic properties of blood and risk of cardiovascular diseases.

According to official statistical data there is a significant difference between pre-menopausal women and age-matched men in morbidity and mortality from cardiac diseases and especially from myocardial infarction. There are several speculations regarding the nature of this phenomenon which have both supporting and refuting evidence. Our hypothesis was that due to regular physiologic bleeding, rheological properties of blood of pre-menopausal women are superior to those of men, and place such women at a lower risk of cardiovascular diseases than men in any age group. We believe that this difference in hemorheological properties is due to the reduced concentration of red blood cells (RBCs) and due to greater population of younger and less population of older RBCs in female blood. We studied mechanical properties of blood from 47 pre-menopausal women and 50 age-matched men. Compared to female blood, male blood had higher viscosity and RBC aggregation and lower RBC deformability. Oxygen Delivery Index, calculated as a ratio of hematocrit to blood viscosity, was found to be significantly lower in male blood. Decreased oxygen delivery along with increased RBC aggregation and decreased RBC deformability may contribute to the higher risk for the development of cardiovascular diseases. Regular blood donation may reduce hematocrit and blood viscosity, improve rheological properties of blood, and increase oxygen delivery in men.