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Out of the Haze of Chemo Brain

CURE, Canadian EditionSummer 2019
Volume 1
Issue 1

Cancer brain fog, or chemo brain, interferes with daily life for many patients. Help can take the form of mental or physical exercise.

Cancer brain fog — the fuzzy, slow thinking that often accompanies cancer and its treatments — is no picnic.

The condition, referred to in scientific circles as cancer- related cognitive impairment or cancer‐related cognitive dysfunction, can involve trouble with remembering things such as words and problems with attention, problem- solving speed and executive function — the mental processes that enable us to plan, focus, remember instructions and multitask.

For most, it’s a temporary issue that gradually improves over time, but for some the “chemo brain” lingers long after treatment stops. The problem affects upwards of 75 per cent of patients during treatment and 35 per cent for months afterwards.

Studies show correlations between “chemo fog” and changes in brain function through imaging techniques, and it is increasingly recognized by health-care providers.

Nevertheless, there are no medications or standard protocols or programs for treating it, and resources can vary between centres across Canada.

There is help for people with the condition, though. Strategies — mainly physical and mental exercises — exist to help with specific aspects of the problem, and experts recommend that patients ask for them if they aren’t offered.


While the terms “chemo brain” and “chemo fog” are commonly used, “cancer-related brain fog” is a better name for it, says Lori Bernstein, an assistant professor of psychiatry at the University of Toronto who also works in the Department of Supportive Care at Princess Margaret Cancer Centre. “Chemo fog makes it sound like chemotherapy is the sole cause, but it’s not necessarily the cause in everyone. It’s only one of many things that can lead to the problem.”

Its causes can also include other cancer treatments (radiation, targeted drugs, immunotherapies, hormonal therapies or stem cell transplants), low red blood cell counts, poor sleep, fatigue, medications that generate drowsiness such as sleeping pills or pain medications, poor nutrition, dehydration, anxiety and the anesthesia used during surgery. It can even be a side effect of the cancer.

The effects and intensity of cancer- related brain fog vary from person to person. Even people who’ve had the same type of cancer and treatments have different experiences, making the condition difficult to predict.

This uncertainty remains because the exact mechanisms of how chemo brain happens are not well under- stood, Bernstein says.

Still, there is some data about the bodily processes that result in chemo brain. Some studies suggest that cancer treatments may cause central nervous system toxicity, which could have both direct and indirect effects on the brain. A 2017 study on animals by researchers in Alberta supports this, suggesting that chemotherapy leads to a process that essentially causes the brain to age during therapy. In addition, a 2018 study conducted at the University of California Los Angeles with breast cancer survivors found a link between cognitive decline and the biological aging of cells due to chemo- therapy and radiation.

Other studies suggest that inflammation is associated with cancer-related brain fog and may be an effect of medications or simply part of the cancer disease process.

Cognitive problems can occur before chemo- therapy, too. In a study from 2011, researchers at the University of Ottawa did brain scans of women with early-stage breast cancer while they performed neuropsychological tests. The scans were done after the patients had undergone surgery but before they began chemotherapy. Results were compared to those of a group of women who didn’t have cancer. While both groups had similar results on some of the tasks, the breast cancer patients were slower to respond on others and made more mistakes in visuospatial activities. The study showed that cognitive changes started before chemotherapy, as did differences in activity in several parts of the brain.


There are no quick medication fixes to help with brain fog. Some researchers have investigated using medications such as memantine, used in patients with Alzheimer’s disease, but “the jury is still out” on its effectiveness, says Kristin Campbell, a physical therapist and director of the Clinical Exercise Physiology Laboratory at the University of British Columbia.

Campbell is investigating the role of moderate-to-vigorous aerobic exercise, such as walking or cycling, on cognition in patients with brain fog. “There is emerging research suggesting physical activity can improve cognition in patients,” she says.

A 2016 review of 19 studies investigating the effects of physical activity on brain fog in animals and humans found that forms of exercise such as yoga may help reduce both symptoms and inflammation. And a 2017 study on women treated for breast cancer found that moderate-to-vigorous exercise can help ease both chemo brain and fatigue.

Generally, you can’t go wrong with being active to a level that feels comfortable, according to Campbell. Walking is a great place to start, she says, and besides yoga, activities such as gardening or tai chi may help, though there are additional benefits for those who can do more intense aerobic exercise.

“Tell your health-care providers if you are having problems and ask what help is available locally,” Campbell says. Sources of help include occupational or physical therapists, patient counsellors, support groups and psychologists. Some larger cancer centres have programs designed to help with brain fog. Help generally focuses on teaching strategies to cope with brain fog, such as doing memory exercises or creating reminder systems such as using sticky notes.

There are also online resources, including the Princess Margaret Cancer Centre’s “Cancer-Related Brain Fog” booklet, which Bernstein authored. It discusses the condition, causes and practical tips for managing the difficulties brain fog causes.

Patients can also find resources through the Canadian Cancer Survivor Network.

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