Outlook: Newsletter of the Society of Behavorial Medicine

Summer 2021

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Exercise for Cancer-related Cognitive Impairments: Bridging the Research Gaps and Moving Towards Recommendations

Linda Trinh, PhD✉; Dori Pekmezi, PhD✉; and Diane Ehlers, PhD✉; Physical Activity SIG


 

Cognitive impairments are a prominent quality of life complaint among cancer survivors, with those receiving adjuvant chemotherapy at highest risk.1,2 Exercise represents a potential solution. The recent physical activity guidelines for cancer survivors3 indicate strong evidence of physical activity’s benefits for reducing cancer-related fatigue, anxiety, and depression, all key determinants of cancer-related cognitive impairment.4 When considered with the neurocognitive evidence in the aging literature, this evidence provides a compelling argument for exercise training as a treatment for cancer-related cognitive impairment. Unfortunately, the limited number of studies conducted in cancer populations makes it difficult to draw conclusions about the efficacy of exercise for improving cognitive function amid cancer.

Common cognitive complaints (‘chemobrain’ or ‘chemofog’) include difficulties with memory, learning, executive function, and processing speed. Approximately 75% of breast cancer survivors report cognitive changes during treatment and many suffer impairments up to 20 years post-treatment.5 Chemotherapy exposure has been shown to: have direct neurotoxic effects on brain structure and function; trigger inflammatory reactions and elevate levels of cytokines; and alter central nervous system vascularization and blood flow.6,7 As the precise mechanisms underlying the pathophysiology of cancer-related cognitive impairment are still unclear; the investigation of effective prevention and treatment strategies has been limited thus far. Effective interventions are needed to prevent, mitigate, or reverse the debilitating effects of cancer-related cognitive impairment.

There is considerable evidence that older adults without cancer who engage in exercise have enhanced cognitive and brain health compared to inactive older adults.8 Exercise-induced changes in cognitive function may be explained by increases in regional brain volume (e.g., prefrontal cortex, hippocampus), improvements in brain structural integrity, and increases in functional connectivity. Further, these changes may be partially mediated by improvement in cardiorespiratory fitness.9 Importantly, the brain structures/functions and cognitive processes with the strongest evidence of improvement through exercise in aging include those most implicated in cancer.10

Consequently, the research community faces a unique opportunity to build upon the emerging body of research on exercise and cancer-related cognitive impairment.11–14 To do so, exercise studies in cancer populations need to include the following: 1) consistently measure cognitive function as a primary outcome with well-normed objective measures to increase comparison across studies; 2) include brain imaging measures to probe how exercise training has regionally specific effects on the brain; 3) deliver exercise interventions with sufficient duration for cognitive change (e.g., ≥6 months, especially for cardiorespiratory fitness); 4) include active control conditions to match for contact time and potential cognitive impacts of social interaction; 5) distinguish between physical activity and cardiorespiratory fitness in examining the associations between these factors and cognitive and brain health;15 6) test different types of physical activity16 such as aerobic only, strength only, combined exercise, and reduced prolonged sitting; and 7) conduct studies in cancer populations besides breast cancer. These conceptual and methodological recommendations will contribute to the evidence on exercise for enhancing cognitive function in cancer survivors. As such, the evidence may inform clinical practice guidelines for improving cognition and quality of life in people living with cancer.

 

References

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