Effect of healthy aging on cerebral blood flow, CO₂ reactivity, and neurovascular coupling during exercise

Abstract

We sought to make the first comparisons of duplex Doppler ultrasonography derived measures of cerebral blood flow during exercise in young and older individuals, and to assess whether healthy ageing influences the effect of exercise on neurovascular coupling (NVC) and cerebral vascular reactivity to changes in carbon dioxide (CVR). In ten healthy young (23±2yr; mean±SD) and nine healthy older (66±3yr) individuals, internal carotid artery (ICA) and vertebral artery (VA) blood flows were concurrently measured, along with middle and posterior cerebral artery mean blood velocity (MCAvmean and PCAvmean). Measures were made at rest and during leg cycling (75W and 35%Wmax). ICA and VA blood flow during dynamic exercise, undertaken at matched absolute (ICA: young 336±95, older 352±155; VA: young 95±43, older 100±30 ml•min-1) and relative (ICA: young 355±125, older 323±153; VA: young 115±48, older 110±32 ml•min-1) intensities, was not different between groups (p>0.670). The PCAvmean responses to visual stimulation (NVC) were blunted in older versus younger group at rest (16±6 vs 23±7%, p<0.026) and exercise; however, these responses were not changed from rest to exercise in either group. The ICA and VA CVRCO2 were comparable in both groups and unaltered during exercise. Collectively, our findings suggest that; 1) ICA and VA blood flow responses to dynamic exercise are similar in healthy young and older individuals, 2) NVC is blunted in healthy older individuals at rest and exercise, but is not different between rest to exercise in either group, 3) CVR is similar during exercise in healthy young and older groups.

Age-related differences in cerebrovascular responses to cognitive stimulation using a novel method

“…However, two studies of working memory (Madureira et al, 2017) and reading (Stefanidis et al, 2019) based tasks did not find any age-related differences on CBFv response. Several TCD-based studies investigating motor (Orlandi & Murri, 1996), visual (Flück et al, 2014;Nowak-Flück et al, 2018;Zaletel et al, 2005) and working memory (Vermeij et al, 2014) found reduced rather than increased responses.…”

“…Healthy aging is associated with a number of key changes in cerebral function (Murman, 2015). Healthy older adults demonstrate reduced hemispheric lateralization to cognitive tasks (Cabeza, 2002), posterior-anterior shift of cognitive processes (McCarthy et al, 2014), and variable changes to the magnitude of the response to cognitive stimulation Jamadar, 2020;Nowak-Flück et al, 2018;Vermeij et al, 2014). These changes were initially thought to be compensatory, given that cognitive function was comparable to younger adults despite these differences (Berlingeri et al, 2013;Reuter-Lorenz & Cappell, 2008).…”

“…Disruption of NVC processes will result in hypoperfusion, particularly at critical moments of increased cognitive activity where function is required to be maximal (Iadecola, 2017). Studies have thus far found conflicting effects of aging on NVC processes with increased Csipo et al, 2019;Grinband et al, 2017;Jamadar, 2020), reduced (Fabiani et al, 2014;Lipecz et al, 2019;Nowak-Flück et al, 2018;West et al, 2019) and comparable (Madureira et al, 2017;Stefanidis et al, 2019) levels of activation and perfusion with younger individuals. However, this may be as a result of variations in methodologies and techniques, lack of correction for brain volume loss, and different cognitive paradigms used to stimulate responses.…”

Neurovascular coupling and cerebral autoregulation in atrial fibrillation

“…Normally distributed data are presented as mean (SD), while non-normally distributed data are presented as median [interquartile range]. Assuming a 6% SD for NVC as Nowak-Fluck et al., 31 the minimal detectable difference between the groups would be 7% with a sample size of 12 patients in each group, at 80% power and 5% alpha. Assuming a 0.35%/mmHg SD for normalized gain at 0.1 Hz during the repeated squat-to-stand manoeuvre as Smirl et al., 32 the minimal detectable difference between the groups would be 0.28%/mmHg with a sample size of 25 patients in each group, at 80% power and 5% alpha.…”

Measurement of Neurovascular Coupling in Neonates

“…In adults, impaired neurovascular coupling has been described in different pathological conditions like stroke, hypertension, hypotension, autonomic dysfunction, Alzheimer’s disease, diabetes, and traumatic brain injury (Duschek and Schandry, 2004; Girouard and Iadecola, 2006; Azevedo et al, 2011; Vetri et al, 2012; Phillips et al, 2014; Jang et al, 2017). In addition, also smoking and healthy aging are associated with a negative effect on neurovascular coupling (Boms et al, 2010; Tarantini et al, 2017; Nowak-Fluck et al, 2018).…”