Aerobic exercise during chemotherapy boosts self-reported cognitive function and quality of life in breast cancer patients, but objective improvements remain elusive, study finds.

Study: Aerobic exercise and CogniTIVe functioning in women with breAsT cancEr (ACTIVATE): A randomized controlled trial. Image Credit: PeopleImages.com / Yuri A / Shutterstock.com

A recent study published in Cancer assesses the positive impact of aerobic exercise during chemotherapy on cognitive function.

The effects of chemotherapy on cognitive function

Chemotherapy is widely used to treat cancer; however, this treatment can increase the risk of cognitive impairment. Up to 75% of women with breast cancer report chemotherapy-related cognitive impairment (CRCI), including  short- and long-term deficits in memory, concentration, and thinking.

Similarly, objective tests of cognitive function have indicated impairments in executive functioning, working memory, language and verbal ability, and spatial ability following chemotherapy for breast cancer, as compared to either breast cancer patients who have not undergone chemotherapy and cancer-free women.

Aerobic exercise

Among older people, as well as those with mild cognitive impairment (MCI), aerobic exercise can help maintain or improve cognitive function. Although aerobic exercise interventions have been promoted among cancer patients and survivors to improve cognitive outcomes, their effectiveness remains unclear.

To date, over 50 randomized controlled trials (RCTs) have been conducted to investifate the impact of aerobic exercise on cognitive function in cancer patients. However, most of these studies have used small samples with non-generalizable characteristics. Moreover, many of these studies failed to use objective test measures or proper self-report assessments, thus limiting the ability to conclusively determine any improvements associated with this intervention.

About the study

The current study utilized data from the Aerobic exercise and CogniTIVe functioning in women with breAsT cancEr (ACTIVATE) trial conducted in Ottawa and Vancouver, Canada. A total of 57 women with breast cancer ranging from stages I to III who were scheduled to begin chemotherapy were included in the study.

Study participants were randomly assigned to aerobic exercise along with chemotherapy, as compared to usual care followed by aerobic exercise once chemotherapy was completed. Aerobic exercise included both supervised and at-home activity.

The trial lasted for 12 to 24 weeks, depending on the chemotherapy regimen. Thirteen neuropsychological tests were used to objectively assess cognition, along with self-reported cognitive function and the resulting difference in quality of life (QoL).

What did the study show?

Most patients were White, working at least part-time, and earning less than $100,000 Canadian dollars a year. Most study participants completed graduate school education and  had stage II breast cancer.

Coronavirus disease 2019 (COVID-19) restrictions prevented the collection of metabolic data after the intervention in 32 patients, whereas complete data was available for 31 patients. In the exercise group, patients completed an average of 34 out of 43 prescribed sessions, which reflected 88% of these sessions. None of the patients reported any adverse events from the exercise regimens during the trial.

Aerobic capacity and ventilatory threshold data indicated a greater decline from baseline in the control group as compared to the exercise group at -3.6 to -2.4 mL/kg/min, and -0.24 to -0.07 L/minutes, respectively. However, these differences were not statistically significant.

Objective cognitive function did not vary between the exercise and control groups, whereas self-reported cognitive function was improved in four of the six measures of one assessment tool in the exercise group. In the second tool, self-reported cognitive function and its impact on QoL were significantly improved in the exercise group as compared to controls.

Why was there correlation between exercise and cognition?

Several explanations may account for this lack of an observed association. For example, the patients included in the current study may not have experienced significant cognitive declines during chemotherapy. Alternatively, the tests may not have been able to detect small changes in cognitive function or any improvements may have diminished after the exercise and before the testing.

A third hypothesis is that the tests did not measure the type of cognitive deficits present in these patients. These changes may develop earlier or be more accurately discerned by self-reported cognitive performances based on daily functioning in the real world, including readiness to return to work or feeling healthy. 

The intervention period may have been too short to impact the underlying mechanisms of cognitive impairment, such as reduced neurogenesis and synaptic plasticity. Pandemic-related restrictions and changes in protocol may have also impacted the results of the experiment.

Subjective and objective measures of cognitive function reflect meaningful but distinct features of cognitive function that affect self-reported outcomes which makes research on both relevant.”

Cognitive stimulation may be required along with exercise to have the desired effect on neuropsychological performance. This is current practice in early intervention for cognitive rehabilitation in many cancer patients.

Conclusions

Among women being treated with chemotherapy for breast cancer, aerobic exercise initiated at the start of chemotherapy improved self-reported cognitive function and QoL.

These observations support the incorporation of aerobic exercise interventions into the standard care for cancer patients undergoing chemotherapy. However, the study findings do not indicate measurable objective protective effects of aerobic exercise against cognitive impairment related to chemotherapy.

An important practical implication could be that different interventions may be appropriate for objective and subjective cognitive difficulties.”