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Stroke Severity and Stroke Risk Factors Correlate with Blood Viscosity

Study Shows Acute Ischemic Stroke Patients Had 27% Higher Viscosity Than Healthy Controls

Research published in the journal Stroke demonstrates that patients who suffered a stroke within the past seven days had diastolic blood viscosity levels 27% higher than age and gender matched healthy subjects. It was also shown that the increase in viscosity was not merely an acute-phase response to the stroke itself, but that it could also serve as an early warning sign for the occurrence of a stroke. Subjects who had experienced a transient ischemic attack (TIA or “mini-stroke”) also had 27% higher viscosity values and those only with the risk factors for stroke had 19% higher viscosity values than healthy controls. The data reveal the severity of hyperviscosity as: stroke group > transient ischemic attack group > at-risk group > healthy controls.

The results are based on a cross-sectional study of 430 subjects who were classified into four groups: 1) those who had suffered a stroke within the past 7 days (135 subjects), 2) those who had experienced a TIA within the past 14 days (89 subjects), 3) those with recognized risk factors for stroke who had not experienced a stroke or TIA in the past 6 months (115 subjects), and 4) healthy controls (91 subjects).

It was notable that hematocrit remained unchanged across all four study groups. This indicates that there are other factors influencing viscosity, underscoring the fact that hematocrit alone is not an adequate indicator of blood flow. The authors traced the group differences in viscosity to the influence of elevated fibrinogen levels and decreased albumin/globulin (A/G) ratios. Their conclusion was supported by the fact that stroke sufferers had 40% higher fibrinogen levels and 21% lower A/G ratios than controls in their study.

The study authors stated that “this study provides evidence that blood hyperviscosity is present not only in subjects with acute brain infarction, but also in those with risk factors for stroke, and that these abnormalities are, to a considerable degree, chronic... Long term treatment strategies that normalize blood flow properties may decrease the likelihood of stroke in subjects with recognized risk factors for stroke.”


B.M. Coull, et al. The Chronic Blood Hyperviscosity in Subjects With Acute Stroke, Transient Ischemic Attack, and Risk Factors for Stroke. Stroke, 22, 2 (1991) 162-168.


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