Association between cardiorespiratory fitness and cerebrovascular reactivity to a breath-hold stimulus in older adults: influence of aerobic exercise training

• Published in: Journal of applied physiology (1985) 2022-06, Vol.132 (6), p.1468-1479
• Main Authors: DuBose, Lyndsey E, Weng, Timothy B, Pierce, Gary L, Wharff, Conner, Reist, Lauren, Hamilton, Chase, O'Deen, Abby, Dubishar, Kaitlyn, Lane-Cordova, Abbi, Voss, Michelle W
• Format: Article
• Language: English
• Subjects: Aged; Brain - physiology; Cardiorespiratory Fitness; Cerebrovascular Circulation - physiology; Cross-Sectional Studies; Exercise; Humans; Hypercapnia; Magnetic Resonance Imaging - methods; Middle Aged
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00599.2021

Cerebrovascular reactivity (CVR) to a physiological stimulus is a commonly used surrogate of cerebrovascular health. Cross-sectional studies using blood oxygen level dependent (BOLD) neuroimaging demonstrated lower BOLD-CVR to hypercapnia among adults with high compared with lower cardiorespiratory fitness (CRF) in contrast to transcranial Doppler studies. However, whether BOLD-CVR changes following chronic aerobic exercise in older, cognitively intact adults is unclear. This study evaluated relations between BOLD-CVR with CRF (V̇o ) using a cross-sectional and interventional study design. We hypothesized that ) greater CRF would be associated with lower BOLD-CVR in older adults ( = 114; 65 ± 6.5 yr) with a wide range of CRF and ) BOLD-CVR would be attenuated after exercise training in a subset ( = 33) randomized to 3-mo of moderate- or light-intensity cycling. CVR was quantified as the change in the BOLD signal in response to acute hypercapnia using a blocked breath-hold design from a region-of-interest analysis for cortical networks. In the cross-sectional analysis, there was a quadratic relation between V̇o ( = 0.03), but not linear ( = 0.87) and cortical BOLD-CVR. BOLD-CVR increased until a V̇o ∼28 mL/kg/min after which BOLD-CVR declined. The nonlinear trend was consistent across all networks ( = 0.04-0.07). In the intervention, both the active and light-intensity exercise groups improved CRF similarly (6% vs. 10.8%, = 0.28). The percent change in CRF was positively associated with change in BOLD-CVR in the default mode network only. These data suggest that BOLD-CVR is nonlinearly associated with CRF and that in lower-fit adults default mode network may be most sensitive to CRF-related increases in BOLD-CVR. Earlier studies evaluating associations between cardiorespiratory fitness (CRF) and cerebrovascular reactivity (CVR) have demonstrated conflicting findings dependent on imaging modality or subject characteristics in individuals across a narrow range of CRF. This study demonstrates that CRF is nonlinearly associated with CVR measured by blood oxygen level dependent (BOLD) fMRI in a large sample of middle-aged and older adults across a wide range of CRF, suggesting that conflicting prior findings are related to the range of CRFs studied.