Increased Aerobic Fitness Is Associated with Cortical Thickness in Older Adults with Mild Vascular Cognitive Impairment

Abstract

Vascular cognitive impairment (VCI) results from cerebrovascular disease and is the second most common type of cognitive dysfunction. Sub-cortical ischemic vascular cognitive impairment (SIVCI) is the most common form of VCI. Current evidence suggests that increased or maintained cortical thickness might be one mechanism by which aerobic exercise preserves cognitive function in older adults. Whether this is also a potential pathway among older adults with SIVCI is unknown. Therefore, the aim of this secondary analysis of a 6-month proof-of-concept single-blinded randomized controlled trial of aerobic exercise was to investigate the associations between (1) aerobic-induced improvements in aerobic fitness capacity and change in cortical thickness in older adults with mild SIVCI; and (2) change in cortical thickness and changes in executive functions. This is a secondary analysis of neuroimaging data from a randomized controlled trial with 71 older adults with SIVCI who were randomly assigned to either a 6-month thrice-weekly aerobic training program or a 6-month nutrition program (i.e., control). Outcome measures were assessed at baseline and trial completion (i.e., 6 months). Aerobic fitness capacity was assessed with the 6-min walk test (6MWT). Magnetic resonance imaging data were acquired at both measurement points from 28 participants to look at changes in cortical thickness. Executive functions were assessed using (1) the Stroop test, (2) the trail making test (part A&B), and (3) the digit symbol substitution test (DSST). At trial completion, compared with the control group, participants in the aerobic training group showed significantly improved 6MWT performance (p = .037). Improved 6MWT performance was independently and significantly associated with increased change in cortical thickness, after controlling for baseline cortical thickness, baseline age, and baseline MoCA (p = .045). Specifically, change in 6MWT performance was significantly positively associated with change in the right superior temporal gyrus thickness (r = .557, p = .002). Maintenance of cortical thickness was independently and significantly associated with improved processing speed performance on the DSST over the 6-month trial, after controlling for baseline DSST performance, baseline age, and baseline MoCA (p = .014). Specifically, change in DSST performance was significantly positively associated with change in the right superior frontal thickness (r = .595, p = .002). Thus, a 6-month aerobic training program may promote cognitive outcomes in older adults with mild SIVCI by improving aerobic fitness capacity and maintaining cortical thickness.