Purpose: To examine the social, biological, and metabolic associations of plasma viscosity in a large epidemiological study.
Methods: Plasma viscosity was measured from 4548 men and 1837 women that took part in the fifth phase of the Whitehall II Study (1997-1999). Employment grade was used as a measure of social position.
Results: A strong inverse relation between employment grade and plasma viscosity was evident (p < 0.0001). This employment grade gradient was apparent overall, and among non-smokers and when participants with poor health were removed from the analyses. Plasma viscosity was associated with a number of biological factors that are themselves socially determined, including fibrinogen (p < 0.001), triglycerides (p < 0.001), fasting insulin (p < 0.001), and height (p < 0.001). Associations with smoking and alcohol intake were apparent in women. In men a U-shaped curve was apparent such that those drinking between 11 and 24 units/week had the lowest plasma viscosity. Alcohol intake, physical activity, and smoking explained 18% of the grade gradient in men and 40% in women while the biological factors examined accounted for 35% in men and 40% in women.
Conclusion: There is a grade gradient in plasma viscosity which was not fully explained by health related behaviors or measured risk factors for CHD. These data suggest that additional factors that contribute to the rheological properties of plasma may contribute to the explanation for social inequalities in cardiovascular disease.