BACKGROUND: Older cancer survivors are at risk for cognitive decline. Physical activity can improve cognition, and better cognitive function may facilitate greater physical activity.
PURPOSE: We examined the potential bidirectional relationship between cognitive function and physical activity in older breast cancer survivors and controls.
METHODS: The sample included women with newly diagnosed, nonmetastatic breast cancer (n = 395) and women without cancer (n = 374) ages 60-98. Participants were recruited as part of a larger multisite study, assessed prior to systemic therapy, and followed yearly for 36 months. Attention, processing speed, and executive function was measured using six neuropsychological tests, self-reported cognitive function using the Perceived Cognitive Impairments subscale of the Functional Assessment of Cancer Therapy-Cognitive Function , and physical activity using the International Physical Activity Questionnaire-Short Form. Separate random intercepts cross-lagged panel models were used to examine the between- and within-person effects for survivors and controls, controlling for age, education, and study site.
RESULTS: Survivors reported significantly less physical activity than controls at baseline (1,284.92 vs. 2,085.98 MET min/week, p < .05). When survivors reported higher activity, they simultaneously had better objective cognition at 12 months (β = 0.24, p = .04) and reported better perceived cognition at 12 and 24 months (β = 0.25, p = .03), but this relationship was not seen in controls. Cognition did not predict subsequent physical activity or vice versa in either group.
CONCLUSIONS: Cognition and physical activity are cross-sectionally associated in survivors, but the expected prospective relationships were not found.