Associations Between Physical Fitness Indices and Working Memory in Breast Cancer Survivors and Age-Matched Controls

Background: This study examined the effects of cardiorespiratory fitness, heart rate recovery, and physical activity on working memory in breast cancer survivors and age-matched controls. Method: Using a case-control design, 32 women who had received a breast cancer diagnosis and completed primary treatment within the past 36-months (11 radiation only; 21 chemotherapy) and 30 age-matched women with no previous cancer diagnosis completed a n-back continuous performance task commonly used as an assessment of working memory. In addition, cardiorespiratory fitness and heart rate recovery were measured during a submaximal graded exercise test and physical activity was measured using 7-days of accelerometer monitoring. Results: Breast cancer survivors who had received chemotherapy had poorer heart rate recovery (p=.010) and engaged in less physical activity than women who had received radiation only (p=.004) or non-cancer controls (p=.029). Cancer treatment (radiation; chemotherapy) predicted differences in reaction times on the 1-back working memory task (p=.029). However, more rapid heart rate recovery predicted shorter reaction times on the 1-back task in the age-matched control group (p=.002). All participants with greater cardiorespiratory fitness displayed greater accuracy independent of disease status on the 1-back task (p=.017). No significant group differences in reaction times were observed for 2-back target trials between breast cancer survivors and controls. However, greater total physical activity predicted shorter reaction times in breast cancer survivors (radiation, chemotherapy) on the 2-back task (p=.014). In addition, all participants who exhibited more rapid heart rate recovery demonstrated better greater accuracy regardless of disease status (p=.013). Conclusion: These findings support differences in physical activty participation, heart rate recovery, and 1- and 2-back working memory reaction times between breast cancer survivors and age-matched controls. Greater cardiorespiratory fitness, heart rate recovery, and physical activity were positively associated with better working memory performance across conditions.