The effects of physical activity and fatigue on cognitive performance in breast cancer survivors.

Purpose: Research suggests that physical activity may be a promising treatment for cancer-related cognitive impairment; however, evidence is limited by small samples and self-report measures and little is known about the underlying mechanisms. The purpose of this study was to examine the effects of physical activity on cognitive function in a national sample of breast cancer survivors (BCSs) using objective measures. We hypothesized that physical activity's effects on cognition would be indirect through survivors' self-reported fatigue.

Methods: Participants (N = 299; M = 57.51 ± 9.54 years) included BCSs with access to an iPad. Participants wore an accelerometer for seven consecutive days to measure their average daily minutes of moderate-to-vigorous physical activity (MVPA) and completed a battery of questionnaires and neuropsychological tests via an iPad application to measure fatigue and cognitive function. Cognitive function was modeled as two latent factors-executive function and working memory-comprising performance across seven cognitive tasks. A structural equation modeling framework was used to test the hypotheses.

Results: MVPA was associated with less fatigue (γ = 0.19), which, in turn, was associated with faster times on executive function tasks (γ = -0.18) and greater accuracy on working memory tasks (γ = 0.16). The indirect paths from MVPA to cognitive performance were also significant (executive function: β = -0.03, memory: β = 0.03).

Conclusions: Findings suggest that MVPA may be associated with greater executive function and working memory in BCSs. Further, this effect may be partially indirect through cancer-related symptoms (e.g., fatigue). Results emphasize the need for additional scientific investigation in the context of prospective and efficacy trials.