Whole blood viscosity and microvascular abnormalities in Alzheimer's Disease

We hypothesized that abnormalities in hemorheologic parameters, including vessel diameter, flow velocity, and whole blood viscosity (WBV), would be present in Alzheimer's Disease (AD) and would correlate with microvascular abnormalities (vasculopathy). Using the Rheolog(TM), we obtained WBV profiles, measured at shear rates of 1-1,000 s(-1), for 10 AD subjects and age matched non-AD controls. Vessel diameter, flow velocity, and microvascular abnormalities were quantified using computer-assisted intravital microscopy (CAIM) of the conjunctival microcirculation. A Severity Index (SI), scale 0-15, was computed to reflect degree/severity of vasculopathy. AD subjects compared to controls had significantly higher WBV (3.96 +/- 0.29 cP vs. 3.34 +/- 0.05 cP, sheared at 300 s(-1); P < 0.05) and SI (7.00 +/- 2.36 vs. 0.30 +/- 0.70; P < 0.05). WBV was correlated (rho(s) = 0.648; P < 0.05) with SI in AD subjects. These results strongly suggest the simultaneous involvement of hemorheologic abnormalities and systemic vasculopathy in AD.