Author(s): BHERER, L., MAGNAN, P.O., VINCENT, T., BESNIER, B., DUPUY, E., GAGNON, G., MOHAMMADI, H., NIGAM, A., GAYDA, M., Institution: UNIVERSITY OF MONTREAL, Country: CANADA, Abstract-ID: 488

Background: Exercise-related physiological adaptations by which it improves brain function are still poorly known. Some studies, including ours, have shown that change in VO2max is a strong predictor of cognitive benefits, but the underpinning physiological mechanisms are not well documented. This study investigated which VO2max metrics better predict various cognitive functions and brain imaging structural markers known to be altered in aging.
Methods: Ninety adults aged 60 and older performed a maximal cardiopulmonary exercise Test (CPET) using an individualized incremental bike protocol according to the most recent recommendations. CPET key parameters were measured with gas exchange analyze (Quark, Cosmed, Italy) during exercise test. They also participated in an MRI session to acquire T1 brain images (1x1x1 mm, Siemens Skyra 3T). CPET key parameters were VO2max normalized with body mass, lean body mass and in % of predicted value (VO2max/kg, VO2max/LBM, VO2max % pred. Brain imaging involved hippocampal volume (average of left and right sides), total grey matter and T1 Hypointensities volumes normalized by intracranial volume as obtained by the Freesurfer segmentation pipeline (version 7.4).
Results: All VO2max metrics were associated to some extent with global cognition, executive function, verbal and working memory, and processing speed. However, when considering composite scores of cognitive performances, and after controlling for age, sex and education, VO2max/kg (p.<.05) and VO2max/LBM (p.<.01) predicted executive functions, while VO2max % pred was the only significant predictor of verbal memory (p.<.001), and none of the VO2max metrics predicted processing speed. All brain imaging measures predicted executive functions (p.<.05), while only total grey matter (p.<.001) and hippocampal volumes (p.<.05) predicted verbal memory. VO2max/LBM and VO2max % pred predicted all brain imaging measures (p.<.05), while VO2max/kg only predicted T1 Hypointensities (p.<.001). Significant partial mediation effects were independently found for total grey matter (p.<.05) and hippocampal volumes (p.<.05) explaining the association between VO2max/LBM and executive functions.
Conclusion: Results support the notion that VO2max metrics are not equivalent predictors of cognitive functions and brain imaging outcomes, highlighting the importance of consistency in reporting results on the relationship between cardiorespiratory fitness and cognition. These results could also inform on more targeted and personalized exercise intervention to maintain and improve cognition and brain health in seniors.