Sex-dependent differences in rheological properties and the relation of blood viscosity to erythrocyte aggregation indices among morbidly obese patients.

Some studies indicate that obesity is associated with rheological disturbances. Because there are usually sex differences in the type of obesity we decided to evaluate rheological differences between male and female obese patients. We studied 18 morbidly obese men, mean age 43.66 +/- 11.32 years, mean body mass index (BMI) 49.82 +/- 6.03 kg/m2 and 20 obese females, mean age 40.6 +/- 11.86 years, mean BMI 47.41 +/- 8.81 kg/m2. Blood and plasma viscosity measurements were performed using a cone-plate viscometer (Brookfield DV-II). Erythrocyte elongation and red blood cell (RBC) aggregation were measured using the Laser-assisted Optical Rotational Cell Analyser (LORCA). Whole blood viscosity and RBC deformability expressed by the elongation index were significantly higher in obese men. We did not observe differences in plasma viscosity, corrected blood viscosity and aggregation parameters among the obese population. Blood viscosity correlated with selected RBC aggregation indices. We conclude that morbidly obese patients presented sex-dependent differences in some rheological properties. This study indicates a relation between erythrocyte aggregation indices and blood viscosity in obese populations.