Claude Nguyen, MD 
Al Hazzouri AZ, Newman AB, Simonsick E, Sink KM, Tyrrell KS, Watson N, et al. Pulse Wave Velocity and Cognitive Decline in Elders: The Health, Aging, and Body Composition StudyStroke. 2013;44:388-393.

Arterial stiffness is a risk factor for subclinical cardiovascular risk that increases with age.  By contributing to systolic hypertension, arterial stiffness has been shown to promote cerebrovascular disease, in turn influencing cognitive decline.  Previously, pulse wave velocity (PWV), a measure of arterial stiffness using transcranial doppler, has not been consistently shown to correlate with changes in cognition.

Al-Hazzouri et al. looked at the relationship between pulse wave velocity and change in cognitive function over 9 years, using a cohort from the Health, Aging and Body Composition Study (Health ABC).  This is a biracial population that has been prospectively followed starting prior to any functional deficits.  2,488 of these had arterial stiffness measurements at baseline based on PWV.  Cognitive function was assessed using Modified Mini Mental State Examination (3MS).  The 3MS was repeated at years 3, 5, 8, and 10.  They also looked at covariates including race/ethnicity, age, sex, years of education, alcohol consumption, smoking status, cholesterol, diabetic status, coronary disease status, blood pressure, and depression.

The study found that those with higher PWV were associated with lower cognitive score.  Even after correcting for cardiovascular risk factors, ApoE4 allele, and socioeconomic factors, there was still a significant association between PWV and poor cognition: those with middle-range PWV had 40% greater odds of cognitive impairment, while those with higher PWV had 59% greater odds of cognitive impairment.  They also found an association between higher PWV and poor performance on visuo-spatial and language tasks, not on memory or executive function. 
What is remarkable about the study is that prospectively, Al-Hazzouri et al. were able to show a relationship between high PWV and faster cognitive decline over a period of 9 years, even after controlling for traditional causes of arterial stiffness, such as cardiovascular risk.  There was a high dropout rate due to mortality, which may diminish the results; however, this is still the strongest evidence yet of an association between arterial stiffness and cognitive decline.  This provides evidence that interventions targeting hemodynamic stress and cerebral microvasculature may help to delay cognitive decline.