Exploration of the relationships between the ventilatory, cardiac and peripheral determinants of cardiopulmonary fitness and cognitive functions in older adults with cardiovascular risk factors
Authors: Magnan P O , Besnier F , Dupuy E , Gagnon C , Vincent T , Mohammadi H , Klai C , Martin N , Juneau M , Gagnon D , Gauthier C , Vrinceanu T , Nigam A , Gayda M , Bherer L 
Published: June 2024

Abstract

Background
Studies on the associations between cardiorespiratory fitness (VO2max) and cognition have used inconsistent methods, which could explain the variability in the results. Understanding how ventilatory, cardiac and peripheral determinants of VO2max impact cognition would allow us to better prevent cognitive decline.

Purpose
Determine the relationship between the ventilatory, cardiac and peripheral determinants of VO2max and cognitive function in older individuals with cardiovascular risk factors (CVRFs). We hypothesised that cognitive functions will mainly be linked to cardiac determinants.

Methods
141 older individuals (70±6 years) with CVRFs underwent a cardiopulmonary exercise test with cardiac output (Qc) measured by impedance cardiography. Various determinants of VO2max, including ventilatory (alveolar ventilation (VA), oxygen uptake efficiency slope (OUES), minute ventilation/carbon dioxide slope (VE/VCO2)), cardiac (cardiac power (CP)) and peripheral determinants (oxygen uptake to workload slope (VO2/Watts) and arteriovenous difference in O2 (C(a-v)O2)) were calculated [1-3]. Participants completed a neuropsychological test battery assessing global cognition (MoCA), working memory (WM), processing speed (PS), executive function (EF) and verbal memory (VM) for which composite z-scores were computed. Simple correlations between VO2max determinants, age, sex and years of education with the MoCA and cognitive scores were carried out. A forward stepwise linear regression was then used to identify predictors of the MoCA and cognition out of all the VO2max determinants, age sex and education. Variables were added based on the p-values and a p&lt;.05 was used to set the limit of variables included in the model.

Results
The MoCA was correlated with both VA (r=.2254, p=.008) and education (r=.1888, p=.028). WM was associated with the VO2/Watts (r=.1941, p=.025) while higher Qc (r=-.2634, p=.009) and CP (r=-.2374, p=.015) correlated with better PS. EF was linked to ventilatory and cardiac determinants of VO2max, including VA (r=-.3742, p≤.001), OUES (r=-.1769, p=.045), VE/VCO2 (r=.2905, p≤.001), Qc (r=-.3074, p=.001), CP (r=-.3027, p≤.001) and age (r=.4355, p≤.001). VM was correlated with CP (r=.2136, p=.024), age (r=-.2475, p=.005) and sex (r=-.4483, p≤.001). Stepwise linear regressions indicated that VO2max determinants had different predictive values on cognitive outcomes (see Table 1).

Conclusion
PS and VM were correlated with peak exercise cardiac parameters, while the MoCA and WM were associated with peak exercise ventilatory and peripheral determinants respectively. EF was linked to peak exercise ventilatory, cardiac and peripheral determinants. Qc predicted both PS and EF while VO2/Watts predicted WM. This indicates that in older individuals with CVRFs the different determinants of VO2max are associated with distinct cognitive functions. These results can inform specific therapeutic targets to maintain optimal cognition in ageing. Stepwise regressions results.