The influence of baseline sleep on exercise-induced cognitive change in cognitively unimpaired older adults: A randomised clinical trial.

OBJECTIVES: Observational studies consistently demonstrate that physical activity is associated with elevated cognitive function, however, there remains significant heterogeneity in cognitive outcomes from randomized exercise interventions. Individual variation in sleep behaviours may be a source of variability in the effectiveness of exercise-induced cognitive change, however this has not yet been investigated. The current study aimed to (1) investigate the influence of a 6-month exercise intervention on sleep, assessed pre- and post-intervention and, (2) investigate whether baseline sleep measures moderate exercise-induced cognitive changes. METHODS: We utilised data from the Intense Physical Activity and Cognition (IPAC) study (n = 89), a 6-month moderate intensity and high intensity exercise intervention, in cognitively unimpaired community-dwelling older adults aged 60-80 (68.76 ± 5.32). Exercise was supervised and completed on a stationary exercise bicycle, and cognitive function was measured using a comprehensive neuropsychological battery administered pre- and post-intervention. Sleep was measured using the Pittsburgh sleep quality index. There was no effect of the exercise intervention on any sleep outcomes from pre- to post-intervention. RESULTS: There was a significant moderating effect of baseline sleep efficiency on both episodic memory and global cognition within the moderate intensity exercise group, such that those with poorer sleep efficiency at baseline showed greater exercise-induced improvements in episodic memory. CONCLUSIONS: These results suggest that those with poorer sleep may have the greatest exercise-induced cognitive benefits and that baseline sleep behaviours may be an important source of heterogeneity in previous exercise interventions targeting cognitive outcomes.

The Effect of Self-Paced Exercise Intensity and Cardiorespiratory Fitness on Frontal Grey Matter Volume in Cognitively Normal Older Adults: A Randomised Controlled Trial.

OBJECTIVE: Exercise has been found to be important in maintaining neurocognitive health. However, the effect of exercise intensity level remains relatively underexplored. Thus, to test the hypothesis that self-paced high-intensity exercise and cardiorespiratory fitness (peak aerobic capacity; VO2peak) increase grey matter (GM) volume, we examined the effect of a 6-month exercise intervention on frontal lobe GM regions that support the executive functions in older adults. METHODS: Ninety-eight cognitively normal participants (age = 69.06 ± 5.2 years; n = 54 female) were randomised into either a self-paced high- or moderate-intensity cycle-based exercise intervention group, or a no-intervention control group. Participants underwent magnetic resonance imaging and fitness assessment pre-intervention, immediately post-intervention, and 12-months post-intervention. RESULTS: The intervention was found to increase fitness in the exercise groups, as compared with the control group (F = 9.88, p = <0.001). Changes in pre-to-post-intervention fitness were associated with increased volume in the right frontal lobe (ß = 0.29, p = 0.036, r = 0.27), right supplementary motor area (ß = 0.30, p = 0.031, r = 0.29), and both right (ß = 0.32, p = 0.034, r = 0.30) and left gyrus rectus (ß = 0.30, p = 0.037, r = 0.29) for intervention, but not control participants. No differences in volume were observed across groups. CONCLUSIONS: At an aggregate level, six months of self-paced high- or moderate-intensity exercise did not increase frontal GM volume. However, experimentally-induced changes in individual cardiorespiratory fitness was positively associated with frontal GM volume in our sample of older adults. These results provide evidence of individual variability in exercise-induced fitness on brain structure.

A Randomized Controlled Trial of High-Intensity Exercise and Executive Functioning in Cognitively Normal Older Adults.

BACKGROUND: There is a paucity of interventional research that systematically assesses the role of exercise intensity and cardiorespiratory fitness, and their relationship with executive function in older adults. To address this limitation, we have examined the effect of a systematically manipulated exercise intervention on executive function. METHODS: Ninety-nine cognitively normal participants (age = 69.10 ± 5.2 years; n = 54 female) were randomized into either a high-intensity cycle-based exercise, moderate-intensity cycle-based exercise, or no-intervention control group. All participants underwent neuropsychological testing and fitness assessment at baseline (preintervention), 6-month follow-up (postintervention), and 12-month postintervention. Executive function was measured comprehensively, including measures of each subdomain: Shifting, Updating/ Working Memory, Inhibition, Verbal Generativity, and Nonverbal Reasoning. Cardiorespiratory fitness was measured by analysis of peak aerobic capacity; VO2peak. RESULTS: First, the exercise intervention was found to increase cardiorespiratory fitness (VO2peak) in the intervention groups, in comparison to the control group (F =10.40, p≤0.01). However, the authors failed to find mean differences in executive function scores between the high-intensity, moderate intensity, or inactive control group. On the basis of change scores, cardiorespiratory fitness was found to associate positively with the executive function (EF) subdomains of Updating/Working Memory (ß = 0.37, p = 0.01, r = 0.34) and Verbal Generativity (ß = 0.30, p = 0.03, r = 0.28) for intervention, but not control participants. CONCLUSION: At the aggregate level, the authors failed to find evidence that 6-months of high-intensity aerobic exercise improves EF in older adults. However, it remains possible that individual differences in experimentally induced changes in cardiorespiratory fitness may be associated with changes in Updating/ Working Memory and Verbal Generativity.