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.