Microvascular abnormalities and whole blood viscosity in Alzheimer's disease

Abstract

Microvascular abnormalities (MA) and whole blood viscosity (WBV) in Alzheimer's disease (AD) patients have been studied for direct correlation. Computer-assisted intravital microscopy (CAIM) was used to objectively quantify MA in the conjunctival microcirculation in AD patients (n=12), using healthy volunteers as control subjects (n=10). Fifteen recognizable MA existed in various vascular diseases, and 10 were commonly found in AD patients, though not all in the same patient. In addition, MA were not found in control subjects. A severity index (SI) -- the arithmetic sum of MA in each patient quantified via CAIM -- was computed to give an objective and quantitative score to correlate with medical history, disease severity, WBV and shear rates. AD SI (7.2±2.8) differed significantly (P<0.05) from control SI (0.6±0.7) and correlated significantly with disease severity. The RheologTM, a computer-assisted scanning rheometer, was used to generate a WBV profile over a 1 to 1,000s−1 range of shear rates. AD WBV (at various shear rates) differed significantly from control values. For example, AD WBV at a shear rate of 300s−1 (3.81±0.37cp) differed significantly (P<0.05) from control subjects (3.34±0.05cp). AD WBV correlated with SI and disease severity, but not with duration of the disease since diagnosis. This finding is intriguing as it indicates that SI and WBV, when combined, may represent a unique availability of correlated quantitative markers with which to predict disease progression or outcome. Funded by a discretion gift from Rheologics, Inc. and a UC Davis Faculty Research Award.