Hemorheological mechanisms in Alzheimer's disease

Objective: The aim of this present study was to elucidate the underlying mechanisms responsible for hamorheological abnormalities in elderly patients with Alzheimer's disease (AD). Subjects and Methods: Twenty-one patients with AD and twenty-three age-matched healthy controls (CON) were studied. We used a controlled-shear rate rheometer generating various flow-fields in vitro for simulating blood flow in vivo. The applied experimental techniques provided valid and quantative data for the analysis of haemorheological parameters, including blood viscosity, erythrocyte deformability, erythrocyte aggregation and oxygen transport efficiency of blood were assessed. Results: The results show no statistically significant difference in most of the blood biochemical parameters between the AD patients and the CON, except that fibrinogen concentration and mean corpuscular cell volume level erythrocytes (MCV) were significantly higher in the AD patients. Hemorheological parameters including blood viscosity, and blood viscoelasticity in the AD patients were considerably higher than the respective factors in the CON. Owing to the MDA levels of the AD patients being significantly higher than that of the CON, the AD patients also showed a decrease in erythrocyte deformability and an increase in blood flow resistance despite the lack of any significant difference in erythrocyte rigidity. In addition, the erythrocyte aggression of AD patients was higher than that of the CON and reduced oxygen transport efficiency was observed in the AD patients. Conclusions: The hamorheological abnormalities found in the AD patients may be explained by the parallel findings of oxidative damage on erythrocyte membranes that could result in a decrease of erythrocyte deformability. Furthermore, the oxidative stress-induced elevation of fibrinogen concentration could lead to accelerated erythrocyte aggression as a consequence of a rise in blood flow viscoelasticity. Taken together, these factors may impair the oxygen transport efficiency of blood in AD patients.