Abstract
BackgroundPhysical inactivity has been consistently linked to increased risk of cognitive decline; however, studies examining the impact of exercise interventions on cognition have produced inconsistent findings. Some observational studies suggest exercise intensity may be important for inducing cognitive improvements; however, this has yet to be thoroughly examined in older adult cohorts. The objective of the current study was to evaluate the effect of systematically manipulated high-intensity and moderate-intensity exercise interventions on cognition.MethodsThis multi-arm pilot randomised clinical trial investigated the effects of 6 months of high-intensity exercise and moderate-intensity exercise, compared with an inactive control, on cognition. Outcome measures were assessed at pre- (baseline), post- (6 months), and 12 months post-intervention. Ninety-nine cognitively normal men and women (aged 60–80 years) were enrolled from October 2016 to November 2017. Participants that were allocated to an exercise group (i.e. high-intensity or moderate-intensity) engaged in cycle-based exercise two times per week for 6 months. Cognition was assessed using a comprehensive neuropsychological test battery. Cardiorespiratory fitness was evaluated by a graded exercise test.ResultsThere was a dose-dependent effect of exercise intensity on cardiorespiratory fitness, whereby the high-intensity group experienced greater increases in fitness than the moderate-intensity and control groups. However, there was no direct effect of exercise on cognition.ConclusionsWe did not observe a direct effect of exercise on cognition. Future work in this field should be appropriately designed and powered to examine factors that may contribute to individual variability in response to intervention.Trial registrationThis study is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12617000643370). Registered on 3 May 2017—retrospectively registered. https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=372780
Highlights
Physical inactivity is considered one of the greatest modifiable risk factors for dementia [1]; attempts to provide definitive evidence from randomised controlled trials (RCTs) of a link between exercise and enhanced cognition have been inconsistent
These conflicting results indicate the need for greater clarity for the use of exercise as a method for preventing cognitive decline, the precise parameters needed for improving brain health
Based on the hypothesis that increases in cardiorespiratory fitness are an important factor in the relationship between exercise and cognition, we investigated whether change in fitness is associated with improved cognition
Summary
Physical inactivity is considered one of the greatest modifiable risk factors for dementia [1]; attempts to provide definitive evidence from randomised controlled trials (RCTs) of a link between exercise and enhanced cognition have been inconsistent. While a more recent meta-analysis [3], assessing a similar cohort, identified positive effects of exercise when session durations were in excess of 45 min and at least of moderate intensity. These conflicting results indicate the need for greater clarity for the use of exercise as a method for preventing cognitive decline, the precise parameters needed for improving brain health. Previous work in the area is promising, the importance of exericise intensity in enhancing cognitive health requires rigorous examination in RCTs. A recent 12-week intervention in older adults demonstrated greater improvements in memory after undertaking high-intensity compared with moderate-intensity exercise, or a stretching control [8]. The objective of the current study was to evaluate the effect of systematically manipulated high-intensity and moderate-intensity exercise interventions on cognition
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