Carotid pulse pressure and intima media thickness are independently associated with cerebral hemodynamic pulsatility in community-living older adults
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Vascular aging is associated with markers of cerebrovascular impairment. Whether discrete characteristics of arterial structure and function have independent and/or additive effects on cerebral hemodynamics, however, is not completely understood. We examined the association of cerebral hemodynamics with common carotid artery intima-media thickness (IMT) and pulse pressure (PP) in 61 older adults with prevalent cardiometabolic risk but no history of cerebrovascular disease. We calculated pulsatility index (PI) and hypercapnic reactivity of the middle cerebral artery, as well as global blood flow through the extracranial arteries. The dominant effects were related to hemodynamic pulsatility. In adults with metabolic syndrome, PI was related to IMT (r = 0.48, P = 0.003) after adjustment for age and sex. Without metabolic syndrome, PI was directly related to PP (r = 0.63, P = 0.003). Across the whole cohort, PP [β (95%CI) = 0.42 (0.18, 0.67), P = 0.001] and IMT [0.42 (0.18, 0.67), P < 0.001] remained significant predictors of PI, after accounting for individual cardiometabolic risk factors. The independent and combined effects of IMT and PP were tested by binarizing PP and IMT at the sample median. Participants with both IMT and PP above their respective medians had elevated PI compared with those with both vascular markers below the median [median (interquartile range) = 1.06 (0.22) vs. 0.84 (0.14), P = 0.003)]. PI was not different from the low risk group if only one of IMT or PP were above the median. Although overall vascular burden was low, moderate associations with PI persisted, suggesting pulsatile characteristics represent one of the earliest markers linking vascular aging to changes in brain health.
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