Cerebrovascular Reactivity and Cognitive Function in Hypertensive and Non‐Hypertensive Adults

Abstract

Hypertension and its vascular consequences contribute to cognitive dysfunction. Accelerated cerebrovascular aging in hypertension may impair cognitive function by impairing cerebrovascular reactivity. Cerebrovascular reactivity in hypertension is often assessed by manipulating CO2, which may not directly reflect reactivity occurring from changes in metabolic supply and neuronal demand during a cognitive task (i.e. neurovascular coupling). The purpose of this study was to compare macro‐ and microvascular hemodynamics at rest and during cognitive activity (Stroop task) in 30 middle‐aged, medicated hypertensive (HTN) and 30 age‐, sex‐, and body mass index (BMI)‐matched non‐HTN adults (56±6 yrs, BMI 28.2±2.9 kg/m2; 32 men). Brachial mean pressure (MP) was measured from an oscillometric cuff. Macrovascular measures included common carotid artery (CCA) mean blood flow from ultrasound and middle cerebral artery (MCA) mean blood velocity from transcranial Doppler. Conductance was calculated as blood flow and mean velocity relative to MP for CCA and MCA, respectively. Microvascular measures included prefrontal cortex (PFC) oxy‐(O2Hb) and deoxyhemoglobin (HHb), and tissue saturation index (TSI) via near‐infrared spectroscopy. Data were analyzed using a 2×2 repeated measures ANOVA but are expressed as change from baseline. Accuracy and hit reaction times were computed to assess cognitive performance. Stroop accuracy (Non‐HTN 95±4%, HTN 95±3%) and reaction time (Non‐HTN 960±142 ms, HTN 998±148 ms) were similar between groups (p>0.05). CCA and MCA conductance were not altered during Stroop (p>0.05). PFC HHb decreased similarly in both groups (p<0.05), while TSI response during Stroop tended to differ (p=0.09) between groups. A significant interaction revealed HTN increased O2Hb during Stroop, while O2Hb was unaltered in Non‐HTN. Differences in O2Hb responses remained when expressed relative to MP. Changes in PFC TSI were positively associated with Stroop accuracy in HTN (r=0.41, p<0.05) but not Non‐HTN (r=0.16, p>0.05). Our data indicate that HTN and Non‐HTN have similar pressure‐mediated macrovascular hyperemia to cognitive activity resulting in a maintenance of macrovascular conductance. HTN exhibit greater increases in O2Hb to achieve similar cognitive performance compared to Non‐HTN, perhaps suggestive of early cerebral aging in HTN. The augmented O2Hb response may contribute to overall tissue oxygenation (TSI) which is associated with preserved cognitive performance in HTN.Support or Funding InformationSupported by an AHA Pre‐Doctoral Fellowship and Foundation Research Grant from ACSMThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.