Abstract
Impaired mobility is a major concern for older adults and has significant consequences. While the widely accepted belief is that improved physical function underlies the effectiveness of targeted exercise training in improving mobility and reducing falls, recent evidence suggests cognitive and neural benefits gained through exercise may also play an important role in promoting mobility. However, the underlying neural mechanisms of this relationship are currently unclear. Thus, we hypothesize that 6 months of progressive aerobic exercise training would alter frontoparietal network (FPN) connectivity during a motor task among older adults with mild subcortical ischemic vascular cognitive impairment (SIVCI)—and exercise-induced changes in FPN connectivity would correlate with changes in mobility. We focused on the FPN as it is involved in top-down attentional control as well as motor planning and motor execution. Participants were randomized either to usual-care (CON), which included monthly educational materials about VCI and healthy diet; or thrice-weekly aerobic training (AT), which was walking outdoors with progressive intensity. Functional magnetic resonance imaging was acquired at baseline and trial completion, where the participants were instructed to perform bilateral finger tapping task. At trial completion, compared with AT, CON showed significantly increased FPN connectivity strength during right finger tapping (p < 0.05). Across the participants, reduced FPN connectivity was associated with greater cardiovascular capacity (p = 0.05). In the AT group, reduced FPN connectivity was significantly associated with improved mobility performance, as measured by the Timed-Up-and-Go test (r = 0.67, p = 0.02). These results suggest progressive AT may improve mobility in older adults with SIVCI via maintaining intra-network connectivity of the FPN.
Highlights
Impaired mobility is a major concern for older adults and is associated with increased risk for disability, institutionalization, and death (Rosano et al, 2008)
Among the 70 randomized individuals in the parent study, we observed a significant effect of aerobic training (AT) on 6-min walk performance, a well-established tool that accurately evaluates cardiovascular fitness (Cataneo et al, 2010) (B = 30.34, p = 0.02), indicating that AT had a positive effect on cardiovascular capacity (Liu-Ambrose et al, 2016)
Bivariate correlation across the study sample showed that the change in frontoparietal network (FPN) connectivity during right tapping was significantly associated with change in 6-Minute Walk Test performance (r = −0.43, p = 0.05; Table 6)
Summary
Impaired mobility is a major concern for older adults and is associated with increased risk for disability, institutionalization, and death (Rosano et al, 2008). In a proof-of-concept randomized controlled trial, we demonstrated that a home-based exercise signficantly reduced falls by 47% in older adults – in the absence of significant improvement in physical function (i.e., balance and muscle strength) (Liu-Ambrose et al, 2008). Significant improvement in executive functions were observed in the exercise group as compared with the usual care (i.e., control) group These data suggest that exercise may reduce falls in older adults via several mechanisms, not just via improved physical function. Using functional magnetic resonance imaging (fMRI) data from a 6-month single-blind randomized controlled trial (clinicaltrials.gov Identifier: NCT01027858), we conducted a planned secondary analysis to assess the impact of moderateintensity aerobic exercise training on functional connectivity of FPN among older adults with mild SIVCI. The primary results from the parent study have been published (Liu-Ambrose et al, 2016), which provided preliminary evidence that 6 months of thriceweekly progressive aerobic training (AT) promotes cognitive performance in community-dwelling adults with mild SIVCI, relative to usual care plus education
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