Cardiorespiratory Fitness Modifies the Relationship Between Arterial Stiffness and Cerebral Blood Flow Independent of Physical Activity

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ABSTRACT INTRODUCTION Central arterial stiffness and cerebral blood flow (CBF) are inversely related. Poor cardiorespiratory fitness (CRF) and low physical activity (PA) are related to both higher arterial stiffness and lower CBF. The present study examined (i) whether CRF or PA moderate the relationship between arterial stiffness and CBF and (ii) whether the intensity or the type of PA need to be considered. METHODS Participants (N=78, Mean AGE =64.2±6.14, 72% female) from the Wisconsin Registry for Alzheimer’s Prevention and the Wisconsin Alzheimer’s Disease Research Center were categorized into low, average and high fitness groups based on maximal graded exercise treadmill test performance. PA was assessed using the CHAMPS questionnaire. Based on hours/week, participants were classified as meeting the recommended 2.5 hours of moderate intensity PA per week (PA Rec Met). Weekly hours of moderate and low intensity PA were calculated as activities of > 3 or < 3 metabolic equivalents, respectively. Activity type was categorized as exercise-, sports/leisure- and work-related. Arterial stiffness was measured as aortic pulse wave velocity (aoPWV) by 2D phase contrast MRI. CBF was assessed by 4D flow MRI in the internal carotid arteries (ICAs), cavernous ICAs, middle cerebral arteries (MCAs), and via two composite measures of total and global flow. RESULTS The association between aoPWV and CBF differed by fitness levels, with a negative relationship in the low fitness group and positive relationships in the average and high fitness groups (all P s<0.05). Significant moderating effects on the relationships between aoPWV and CBF were also observed for PA Rec Met (all P s<0.05), moderate intensity ( P =0.05) and exercise-related (all P s<0.02) PA. DISCUSSION Average or high fitness, meeting the PA guidelines, and more specifically, moderate intensity and exercise-related PA seem to attenuate the negative relationship between aoPWV on CBF.

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