December 29, 2017
5 min read

Physical activity may reduce fatigue, improve cognitive function among breast cancer survivors

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Diane K. Ehlers

Physical activity appeared associated with reduced fatigue and increased performance on cognitive tests among a cohort of breast cancer survivors, according to study results.

Cognitive impairment — such as memory problems or shortened attention spans — is a common complaint among patients with cancer and cancer survivors. However, little is known about the cause, as data are limited by small sample sizes and self-reported measures.

Diane K. Ehlers, PhD , assistant professor in the department of exercise science at Arnold School of Public Health at University of South Carolina, and colleagues from her previous institution — University of Illinois — assessed the effects of physical activity on cognitive function among 300 breast cancer survivors.

Results showed moderate to vigorous physical activity appeared associated with decreased fatigue, which — in turn — appeared linked to shorter times on executive function tasks and greater accuracy on working memory tasks.

“Other studies of cancer survivors have relied on small samples of cancer survivors, and used self-reporting measures of physical activity and cognitive function, which can be very biased,” Ehlers said in a press release. “What makes our study novel is that we had objective measures for both physical activity and cognitive performance, as well as a nationwide sample of breast cancer survivors.”

HemOnc Today spoke with Ehlers about the study, the potential implications of the results and the recommendations clinicians should make to their patients.


Question: Can you describe the prevalence of fatigue and cognitive impairment among individuals who undergo cancer treatment?

Answer: Fatigue is definitely a well-studied outcome of cancer treatment because it affects the vast majority of patients with cancer. In terms of cognitive impairment, this has been around for a while, but its presence is now growing in clinical research. The reason for this is that it is most often self-reported. Researchers are now confirming that these self-reports are real and that the idea of ‘chemo-brain’ is real. Clinicians are increasingly recognizing that this is a problem.


Q: What prompted this research?

A: When I was at University of Illinois, I worked with Edward McAuley, PhD, professor in the departments of kinesiology and psychology, and his longtime collaborator, Art Kramer, PhD, director of Beckman Institute for Advanced Science and Technology and Swanlund chair and professor of psychology and neuroscience. The two have worked together for nearly 30 years on the effects of physical fitness on cognitive function and brain health in older adults. They have provided a significant amount of evidence on the effects of exercise on cognitive function and brain health in older adults. The suggestion in the literature is that the biological pathway for cancer and cognition is similar to the pathway for aging and cognition. Therefore, we thought treatments used for older adults might be useful for patients with cancer and cancer survivors. Although we are not the first to assess this, we did have the data from prior aging studies to back up our hypothesis. We also had a technology company, Digital Artefacts in Iowa City, agree to develop a tailored version of their previously established neuroscience app known as BrainBaseline. They helped us build an iPad app that included their BrainBaseline cognitive tests and questionnaires we wanted to share with study participants.



Q: How did you conduct the study?

A: We recruited women diagnosed with breast cancer from across the country. All participants had access to an iPad. We asked study participants to complete a set of questionnaires and cognitive tests that assessed the various domains of cognitive functioning within 2 weeks of signing up for the study. We also asked participants if they would be willing to wear an activity tracker. We ended up with valid physical activity data from the trackers for about 300 women.


Q: What did you find?

A: We looked at the associations between daily minutes of moderate to vigorous physical activity and performance on cognitive tests that measured executive function and working memory. We found that more daily minutes of moderate to vigorous physical activity were associated with faster performance on the tests that measured attention, as well as higher accuracy on tests that measured memory. We also looked at the role that fatigue may have played in this relationship because frameworks of cancer-related cognitive impairment have suggested fatigue as one determinant, and physical activity is known to improve cancer-related fatigue. We found that more physical activity was related to less fatigue. Less fatigue, in turn, was associated with better performance on cognitive tests. We do not know a lot about the mechanisms of the relationship between physical activity and cancer-related cognitive impairment. This provides us with some evidence that fatigue may be one of the mechanisms along the pathway.


Q: What are the clinical implications of the findings?

A: Fatigue is very well studied and documented in relation to physical activity. In the exercise oncology literature, we have so many studies in support of physical activity as a treatment for cancer-related fatigue. Therefore, we already have interventional models that might also be beneficial to cancer-related cognitive impairment. We may be able to pull from the physical activity/fatigue literature to design some of our interventions aimed at improving cognition in these populations. We may not have to ‘reinvent the wheel’ after all.


Q: Did any of your findings surprise you?

A: We did not expect to see a direct effect of physical activity on cognitive function. This probably just means that there are other mechanisms at play and that fatigue is not the only one responsible. Some of the other potential mechanisms we plan to explore in future studies include brain structure, function and inflammation.



Q: Does more research need to be conducted?

A: Definitely. This study was cross-sectional, and we think it was a strong study in some respects because the national sample of breast cancer survivors was a large cohort compared with other studies that have been conducted. We also used objective measures of physical activity and cognitive functioning, as well as stronger methods of statistical analysis. We created executive function and working memory factors that were comprised of multiple cognitive tests, which gives stronger weight to the conclusions we drew. However, there are study limitations, including our sample being mostly white, well educated and having high income. Therefore, we do not have an understanding of the effects of physical activity on cognitive functioning among minority breast cancer survivors and those who are less educated. We need more prospective studies and a diverse sample of patients. We are recruiting a second cohort for this study through which we will target racial and ethnic minorities who either have breast cancer or are breast cancer survivors. We will use an iPhone-based platform this time. More information about this effort is available at


Q: Is there anything else that you would like to mention?

A: Although physical activity is not a magical cure, it does offer many benefits for cancer survivors. It is a nonpharmacological treatment that is available to most people. I think this evidence shows it is a no-brainer that physical activity needs to be added to the standard of care for these patients. – by Jennifer Southall



Ehlers DK, et al. Breast Cancer Res Treat. 2017;doi:10.1007/s10549-017-4363-9.


For more information:

Diane K. Ehlers , PhD, can be reached at University of South Carolina, Public Health Research Center, Columbia, SC 29208; email:


Disclosure: Ehlers reports support from a postdoctoral fellowship from American Cancer Society (PF-16-021-01-CPPB) for her work on this study at University of Illinois Urbana-Champaign.