Abstract
Epidemiological
studies suggest a dose-response relationship exists between physical
activity and cognitive outcomes. However, no direct data from randomized
trials exists to support these indirect observations. The purpose of
this study was to explore the possible relationship of aerobic exercise
dose on cognition. Underactive or sedentary participants without
cognitive impairment were randomized to one of four groups: no-change
control, 75, 150, and 225 minutes per week of moderate-intensity
semi-supervised aerobic exercise for 26-weeks in a community setting.
Cognitive outcomes were latent residual scores derived from a battery of
16 cognitive tests: Verbal Memory, Visuospatial Processing, Simple
Attention, Set Maintenance and Shifting, and Reasoning. Other outcome
measures were cardiorespiratory fitness (peak oxygen consumption) and
measures of function functional health. In intent-to-treat (ITT)
analyses (n = 101), cardiorespiratory fitness increased and perceived
disability decreased in a dose-dependent manner across the 4 groups. No
other exercise-related effects were observed in ITT analyses. Analyses
restricted to individuals who exercised per-protocol (n = 77)
demonstrated that Simple Attention improved equivalently across all
exercise groups compared to controls and a dose-response relationship
was present for Visuospatial Processing. A clear dose-response
relationship exists between exercise and cardiorespiratory fitness.
Cognitive benefits were apparent at low doses with possible increased
benefits in visuospatial function at higher doses but only in those who
adhered to the exercise protocol. An individual’s
cardiorespiratory
fitness response was a better predictor of cognitive gains than exercise
dose (i.e., duration) and thus maximizing an individual’s
cardiorespiratory fitness may be an important therapeutic target for
achieving cognitive benefits.
Trial Registration
ClinicalTrials.gov
NCT01129115
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