['This study was carried out to determine whether changes in hemorheological parameters parallel the severity of essential hypertension.', 'A total of 198 older hypertensive patients were recruited and classified into 3 stages of hypertension according to the grading standard of hypertension. The whole blood viscosity (WBV) at various shear rates, plasma viscosity and erythrocyte rheology (including erythrocyte rigidity index, erythrocyte aggregation index and erythrocyte deformation index) were examined.', 'Erythrocyte rheology paralleled the severity of essential hypertension and was significantly correlated to the average 24\xa0h systolic blood pressure and diastolic blood pressure. Logistic analysis revealed that erythrocyte rigidity and the erythrocyte aggregation index were positively correlated with the severity of hypertension, while the erythrocyte deformation index was negatively correlated. No association was found between WBV, plasma viscosity and the severity of hypertension.'] Are erythrocyte rheological properties but not whole blood and plasma viscosity associated with severity of hypertension in older people?