Lost in the fog: Understanding chemobrain


Ashley Henneghan, MSN, BSN, RN, CHPN Doctoral Student & Graduate Research Assistant at the University of Texas at Austin School of Nursing

When I tell people that my research interest (and the focus of my dissertation) is cognitive dysfunction amongst breast cancer survivors, the response I get typically begins with one of the following words: who, what, when, where, why or how.

This reaction makes me think that people, especially those who have been touched by cancer first hand, are hungry for information about this topic. In the following paragraphs I will attempt to satisfy this hunger by touching on some of the most common questions I receive on the topic of cancer-related cognitive dysfunction (CRCD), more commonly referred to as “chemobrain.”

What is cancer-related cognitive dysfunction?

CRCD  or “chemobrain” is one of the most frustrating and devastating effects of cancer and/or cancer treatment. CRCD results from changes in the brain that affect a person’s ability to think, learn new things, recall words, multitask, concentrate, formulate ideas, reason, and remember. Some have described it as mental cloudiness or fogginess. The aspects of cognition most affected by cancer treatments (including those for breast cancer) are executive function, memory, attention, and processing speed. The following is a breakdown of how CRCD can affect each of these abilities and processes.

Executive Functioning

  • A set of cognitive skills used for adaptation and goal oriented behaviors
  • Involves inhibiting responses, being cognitively flexible, and prioritizing tasks
  • Examples include:
    • Struggling with doing several things at one time
    • Difficulty getting started with a task
    • Losing track of what you are thinking, reading, or saying


  • Involves several steps – receiving new information, storing it, and retrieving it (Any of these steps can be affected)
  • Examples include:
    • Forgetting an appointment
    • Inability to remember how to do something or perform a task
    • Forgetting an address or phone number


  • Involves the ability to focus or concentrate
  • Examples include:
    • Difficulty focusing on a task when there are distractions
    • Being forgetful
    • Difficulty staying on task

Processing Speed

  • Also known as reaction time
  • Is connected with other cognitive functions such as attention and memory
  • Survivors have described it as “slow” or “foggy” thinking, inefficient thinking that worsen when tasks are more difficult or when there are more distractions

Where in the brain does CRCD occur?

Studies show that in comparison to the brains of non-cancer patients the frontal areas of survivors’ brains look and function differently. The frontal lobe of the brain is what makes us human in the animal kingdom – it’s what allows us to think and perform complex, cognitive tasks. Additionally, brain changes in the area of the brain primarily responsible for memory as well as in the connections between different brain areas have been reported in the research.

Who gets cancer-related cognitive dysfunction?

For a long time the scientific community believed CRCD only occurred in persons diagnosed with cancers of the central nervous system (CNS). However cancer patients and survivors of non-CNS cancers (such as breast cancer) claimed they experienced similar symptoms.  Researchers soon discovered CRCD in subgroups of breast, prostate, colon, ovarian, testicular, and lung cancers, highlighting another avenue for future research.

Although this is often referred to as “chemobrain, research has shown that cognitive dysfunction can be a side effect of surgery, radiation, biological therapies, and hormonal therapies too.

Approximately 78% of breast cancer patients and survivors experience problems with their cognition at some point during or after their cancer treatment. Due to questionable methods of measuring and quantifying CRCD, it is likely that these estimates fall short of the true incidence in the overall cancer population.

Several risk factors for CRCD have been identified. These include higher age (>60 years old), genetics, lower cognitive reserve (level of education), and exposure to certain treatment types (higher doses of chemotherapy or radiation; combined chemotherapy, surgery, and radiation; doxorubicin based chemo; Tamoxifen).

When does cancer-related cognitive dysfunction occur and when does it get better?

Approximately 35% of breast cancer patients will have CRCD prior to the start of chemotherapy. The majority (up to 78%) experience CRCD during active primary treatment such as surgery, chemotherapy, radiation. Approximately 30% of survivors will exhibit their first cognitive symptoms a year or more after the end of primary treatment.

For many survivors, cognitive symptoms diminish within the first 6-12 months after primary treatment ends; but for some, the effects persist long after active treatment is completed and can even last up to 20 years. For others, their condition may worsen over time.

How does cancer-related cognitive dysfunction affect one’s life?

CRCD has been associated with difficulty performing social roles and engaging in the community, and challenges returning to work or maintaining employment. Survivors report difficulties managing their day-to-day activities, which negatively impacts their overall quality of life.

Why does cancer-related cognitive dysfunction occur?

Scientists do not know why some cancer survivors experience CRCD and others do not. The cause of CRCD is unclear, and it’s likely a combination of factors.  There are several proposed mechanisms that have supportive evidence.

Proposed mechanisms:

Direct Effects: One proposed mechanism is that the cancer in the body directly causes neurological damage. This was proposed after it was discovered that CRCD could occur prior to chemotherapy administration.  It is proposed that chemotherapy can directly access the brain and cause damage.

Genetic predispositions: Another group of researchers has linked a gene with vulnerability to CRCD. Others have proposed that faulty genetic repair mechanisms may be responsible for CRCD.

Oxidative damage: Exposure to environmental toxins and stressors and can damage DNA structures.  Evidence supports that oxidative damage occurs in breast cancer patients. Oxidative damage has been linked with other neurologic disorders such as Alzheimer’s and Parkinson’s diseases.

Estrogen Deprivation: The vast majority of breast cancer survivors experience menopause as a result of treatment. Estrogen has been linked to optimal cognitive functioning in addition to antioxidant effects in the body. Some studies support this mechanism while others do not.

Inflammation: Our immune systems are responsible for repairing damaged neurons in the brain. Often cancer patients and survivors have higher levels of inflammation compared to those without cancer. Studies in both animals and humans have shown that persistent inflammation can lead to cognitive deficits. Inflammation also been linked to other symptoms in cancer survivors such as fatigue, depression, and sleep disturbance.

What can be done about cancer-related cognitive dysfunction?

Unfortunately, CRCD is currently irreversible. The good news is this may change in the near future! In the meantime there are things that can be done to optimize cognitive function such as cognitive remediation, use of compensatory strategies, and lifestyle adjustments.


Cognitive rehabilitation are therapeutic processes provided by trained professionals that target areas of cognitive functioning involved in learning and basic day-to-day functioning. The goals are to bolster individual’s cognitive capacities such as problem-solving and memory. The premise of remediation lies in the idea of the ability for the brain to generate new brain cells and pathways to improve cognitive abilities.  Cognitive remediation (or rehabilitation) can be done in person with a trained healthcare provider or online through various computerized programs such as BrainHQ, Cognifit, and Lumosity.

Alternative Strategies

There are some “work- arounds,” or detours for problematic cognitive processes that cannot be corrected. Some examples include:

  • Using external aids (e.g. smart phones or day planners) to organize, keep track of to do lists, and set alarm reminders
  • Breaking down tasks into smaller manageable steps
  • Keeping a notebook handy to write things down as they come up or using voice recording functions on a smartphone
  • Asking for feedback when talking with others, e.g. “Did I tell you this already?”
  • Minimizing distractions in your work place – closing doors, turning off ringers and email when possible
  • Repeating key points when talking with others to make sure you get the gist of what they are saying
  • Being patient with yourself and allowing more time to complete tasks than you used to

Lifestyle Adjustments and Healthy Behaviors

Cognitive Exercise

  • Exercise your brain like your body on a regular schedule
  • Find something that is challenging to your brain and enjoyable, and do it!
  • Examples include learning a new language or instrument, joining a book club, playing scrabble with friends, watching educational documentaries

Stress Management

  • Chronic stress, anxiety, and depression can worsen cognitive function and quality of life and negatively impact physical and emotional well-being
  • Manage stress with relaxation techniques such as guided meditation and imagery, breathing exercises, yoga, tai chi, muscle relaxation
  • Choose what works for you and make it a regular part of your daily routine- 10-30 minutes a day – the more the better
  • If anxiety and depression are taking over your life, reach out for help

Physical Activity

  • Physical activity has been shown to be so important for cancer survivors. It can reduce stress, improve cognition, help you sleep better, and improve overall survival rates and quality of life.
  • Aim for 150 min of cardiovascular exercise a week for these benefits. Even small steps count!

Maintaining social support

  • Share the information you have learned here with those who support you
  • Having your family and friend’s support will facilitate your healthy behaviors and help keep your stress levels lower

Pain and Insomnia can also impair cognitive function, so if you are experiencing these symptoms, reach out to your health care provider.

Overall, there is growing evidence that cognitive changes occur secondary to cancer and/or cancer treatment.  While we do not have a means of reversing cancer-related cognitive dysfunction, there are steps that survivors can take to enhance their cognitive abilities.  Although it may be discouraging to learn that scientists and clinicians alike do not have all the answers to the questions above, do not lose hope! The scientific community is making significant progress and every day we are learning more about this pervasive and unwanted side effect of cancer and cancer treatment.

Improving CRCD is a high priority in survivorship research and among oncology organizations. Cognitive function relates directly to one’s personal identity and therefore affects all aspects of an individual’s life. Problems with cognition can be frustrating, embarrassing, and devastating especially because physically the person appears “normal” and no one can “see” the problems she or he is experiencing.  My hope is that progress in CRCD research will lead to clinical guidelines to appropriately prevent, treat, and manage cognitive problems and improve survivors’ daily functioning and quality of life.


Posted in
Scroll to Top