Important evidence for the link between blood viscosity and cardiovascular events was provided by the Edinburgh Artery Study in a random population of 1,592 men and women aged 55 to 74 years, who were followed over a mean period of 5 years. After adjustment for age and gender, mean values for both blood viscosity and hematocrit-adjusted blood viscosity were elevated in patients who experienced cardiovascular events (ischemic heart attacks and strokes) relative to those who did not. The differences in blood viscosity were statistically significant (p=0.0003), and the link between blood viscosity and the occurrence of cardiovascular events was at least as strong as that of diastolic blood pressure and LDL cholesterol and stronger than that of smoking. 
In a seminal report just prior to the publication of the Edinburgh Artery Study, Lousiana State University pathologist Gregory Sloop proposed that blood viscosity is the one unifying mechanism by which all established cardiovascular risk factors promote atherosclerosis, including LDL cholesterol, high blood pressure, diabetes, obesity and smoking . Numerous studies have confirmed the linkages between blood viscosity and the following cardiovascular risk factors:
- Hypertension [3-6]
- Hyperlipidema: positive correlation with LDL cholesterol, total cholesterol and triglycerides; negative correlation with HDL cholesterol [7-13]
- Diabetes, insulin resistance syndrome and obesity [12,14-18]
- Tobacco smoking [6,19-21]
- Male gender vs. premenopausal women [12-13,22-23]
- Aging [12,21,24]
In his report, which was titled A Unifying Theory of Atherogenesis, Dr. Sloop indicated that blood viscosity was uniquely suited to predict the entire course of cardiovascular disease because blood viscosity accomplishes the following: (i) accounts for the morphological similarity of atherosclerotic lesions associated with many diverse risk factors, (ii) explains the anatomic distribution of lesions throughout the body, (iii) provides a role for platelet activation by turbulent blood flow caused by hyperviscosity, (iv) includes an explanation of the protective role of HDL cholesterol (i.e., HDL has been shown experimentally to lower viscosity). 
Blood viscosity holds certain similarities with blood pressure. Like blood pressure, the viscosity of blood changes during each cardiac cycle and is reported using two numerical quantities: systolic and diastolic viscosity. However, while blood pressure is parameter of the circulatory system as a whole, blood viscosity is a parameter specific to the fluid flowing through the system. Therefore, viscosity can be said to precede pressure and to be biophysically more fundamental than pressure.
The Blood Viscosity Test is performed at Meridian Valley Lab using a calibrated glass capillary system that is classified as a Class I device under 21 CFR § 862.2920. The Blood Viscosity Test is not covered by insurance plans. Doctors must bill their patients or their patients’ caregivers for this service.