Researchers at La Fe University Hospital in Valencia, Spain found that blood becomes significantly more viscous as people age. The study included 927 healthy patients aged between 16-85 years and patients were separated into four age groups (<30, 30-44, 45-50, ≥60). These findings held true for those with and without cardiovascular risk factors, even after blood samples were standardized for blood viscosity measurements. While the link between cardiovascular risk factors and increased blood viscosity is known, this study demonstrated that aging itself causes a decline of blood flow parameters, likely due to other factors such as inflammation and changes in lipids. People who are otherwise absent of cardiovascular risk factors may have underlying and clinically silent risk as they age because blood viscosity is not a commonly measured in clinical practice.
Vaya A, Alis R, Romagnoli M, et al. Rheological blood behavior is not only influenced by cardiovascular risk factors but also by aging itself. Research into 927 healthy Spanish Mediterranean subjects. Clin Hemorheol Microcirc. Jan 1 2013;54(3):287-296.