Vascular factors have become increasingly recognized to be associated with cognitive impairment and dementia. Dissecting out the relative contribution of hypertension and the interrelated factor of vascular stiffness is of considerable importance because of the increasing prevalence of cognitive impairment and dementia as our population ages and the limited therapeutic options once dementia has developed. The data from Muela and colleauges 1 contend that "higher arterial stiffness is related to cognitive impairment at different levels of hypertension." Furthermore, two different but related measures of arterial stiffness, specifically pulse wave velocity (PWV) and augmentation index, as well as structural properties of the carotid artery-its intimal medial thickness-are associated with lower cognitive performances. Triantafyllidi and colleagues 6 found that impaired cognitive function was associated with increased large artery stiffness in patients with newly diagnosed, untreated hypertension. In multivariate analysis weighted for age, arterial stiffness was the only predictor for MMSE score in a population after adjustment for body mass index, office systolic and diastolic BP and pulse pressure, 24-hour mean systolic and diastolic BP, urine albumin, sex, and atherosclerotic risk factors (smoking, cholesterol, and triglycerides).
6In the Framingham offspring cohort of 1101 participants, with a mean age of 69 years, aortic stiffness assessed by carotid femoral PWV, after adjustment for age and sex, predicted an increased risk of mild cognitive impairment, all-cause dementia, and Alzheimer disease. The ability of vascular stiffness to induce target organ changes independent of the effect of BP is not unique to the brain but occurs in the heart and the kidney. 10,11 There are a number of fundamental mechanisms that can explain the relationship of arterial stiffness and memory impairment. O'Rourke and Safar 11 theorized that the high blood flow and low resistance in the brain "exposes small arterial vessels to the high-pressure fluctuations" thereby producing microvascular damage. Magnetic resonance imaging studies have expanded this concept by demonstrating the associations between aortic stiffness and cerebral microvascular remodeling and microvascular parenchymal damage. 12 These data suggest that increased vascular stiffness,