Blood Viscosity and Elevated Carotid Intima-Media Thickness in Men and Women

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Abstract
Background —Several hemostatic and rheological factors have been associated with incident cardiovascular events. However, there have been no reports on the relationship of rheological factors with early atherosclerosis and very few on hemostatic factors. We therefore studied the relationship between these factors and carotid intima-media thickness (IMT). Methods and Results —The Edinburgh Artery Study measured fibrinogen, tissue plasminogen activator (tPA), fibrin d -dimer, von Willebrand factor (vWF), blood and plasma viscosities, and hematocrit as part of its baseline examination during 1988–1989. At the 5-year follow-up, valid measurements of IMT had been recorded in 1106 men and women 60 to 80 years old. In men, blood viscosity ( P ≤.001) and its major determinants, plasma viscosity, fibrinogen (both P ≤.01), and hematocrit ( P ≤.05), were all linearly related to IMT. Furthermore, blood viscosity, fibrinogen (both P ≤.01), and plasma viscosity ( P ≤.05) remained significantly associated on multivariate analysis. Correcting blood viscosity to a standard hematocrit of 45% had little effect on its association. In men, there was a significantly increased risk of having an IMT above versus below the upper quartile of its distribution (1.05 mm) for SD increases in blood viscosity ( P ≤.01), fibrinogen, corrected blood viscosity, and plasma viscosity (all P ≤.05). With the exception of plasma viscosity, these risks were unaffected by adjustment for other common cardiovascular risk factors. No significant associations were found between any of the hemorheological factors and IMT in women or for tPA, fibrin d -dimer, or vWF in either sex. Conclusions —These findings suggest that in men, blood viscosity and its major determinants are associated not only with incident cardiovascular events but also with the early stages of atherosclerosis. This may be one explanation for the link between rheological factors and events.