Higher Maximal Cardiorespiratory Fitness is Associated with Lower Cerebrovascular Stiffness in Healthy Mid‐Life and Older Adults
Authors: Freeberg Kaitlin A. , McCarty Narissa P. , Seals Douglas R. , Craighead Daniel H. 
Published: April 2020

BackgroundAge‐related impairments in cerebrovascular function likely contribute to cognitive decline with aging. In particular, cerebral artery stiffening with aging leads to transmission of damaging, pulsatile blood flow to the microcirculation, causing suboptimal tissue perfusion and cerebrovascular dysfunction. Conversely, physically active older adults with higher cardiorespiratory fitness (CRF) often have greater cerebrovascular function, as evidenced by greater cerebrovascular reactivity, than sedentary peers. This suggests that either regular physical activity, higher CRF, or both has beneficial effects on the cerebrovasculature and may contribute to preserved cognitive function with aging. However, little is known about the relations between physical activity, as assessed by leisure time physical activity (LTPA), or CRF and cerebrovascular stiffness.PurposeTo determine if cerebrovascular stiffness is related to LTPA, CRF or both among healthy mid‐life and older adults, and if individuals with higher levels of LTPA and/or CRF have greater cerebrovascular stiffness reactivity in response to a vasodilatory stimulus and/or better cognitive function.MethodsCerebrovascular stiffness (pulsatility index, PI), LTPA, CRF and cognitive function were assessed in 27 mid‐life/older adults (12F/15M; 67±1 years) free from chronic diseases and dementia. Middle cerebral artery velocity (MCAv) was measured with a 2‐MHz Doppler probe during 5 minutes of normocapnia and hypercapnia (breathing 5% CO2). PI was defined as (MCAvsystolic‐MCAvdiastolic)/MCAvmean measured over the final 60 seconds of each phase. LTPA was calculated using the Modifiable Activity Questionnaire. CRF was determined by assessing maximal oxygen consumption (VO2max) during incremental treadmill exercise to exhaustion. The cognitive domains of executive function, processing speed, working memory, and language were assessed with the NIH Toolbox Cognition Domain and composite scores for fluid, crystallized, and total cognition were calculated.ResultsPI was inversely related to CRF under both normocapnic (r=0.41, p=0.04) and hypercapnic (r=0.46, p=0.02) conditions, indicating lower cerebrovascular stiffness in those with greater CRF. However, there was no relation between LTPA and PI under normocapnic (r=0.04, p=0.86) or hypercapnic (r=0.12, p=0.55) conditions. There were no relations between the change in PI from normocapnia (baseline) to hypercapnia and CRF (r=0.06, p=0.23) or LTPA (r=0.041, p=0.84). Finally, there were no relations between any measures of cognitive function and PI under either normocapnic or hypercapnic conditions (all p>0.05).ConclusionsThese preliminary results suggest cerebrovascular stiffness is inversely related to CRF, but unrelated to LTPA, among healthy mid‐life/older adults. However, the change in cerebrovascular stiffness in response to a vasodilatory stimulus was not related to CRF, suggesting that absolute cerebrovascular stiffness may be more strongly associated with CRF than functional reactivity. Cognitive performance was not related to CRF or LTPA, likely because subjects were healthy and without cognitive impairments.Support or Funding InformationAHA 18POST33990034