When some individuals undergo chemotherapy, they notice changes in their memory, concentration and the way they think. First reported in women with breast cancer who were undergoing treatment, for years people have worried about, joked about and been frustrated by the mental fogginess that comes with what they've dubbed "chemo brain." For the first time, researchers have been able to demonstrate that chemo brain is a genuine effect.

The study, published in the journal Clinical Neurophysiology, found that people who reported chemo brain lack the ability for sustained focused thought. "A healthy brain spends some time wandering and some time engaged,” said Todd Handy, one of the researchers and a professor of psychology at the University of British Columbia. "We found that chemo brain is a chronically wandering brain, they’re essentially stuck in a shut out mode.”

The researchers found that those with chemo brain tend to stay in this disengaged state. That is the reason why 50% of patients who are thought to be affected feel the need to constantly write things down and keep tasks as simple as possible.

The researchers used an electroencephalogram (EEG), a test that detects electrical activity in the brain, to monitor the brain activity of breast cancer patients while they completed a series of tasks. They discovered that the breast cancer survivors were “less likely to maintain sustained attention” compared to healthy individuals—this was true even up to three years after treatment.

What was even more worrying was that when the women thought they were concentrating, the EEG showed that large parts of their brains were actually turned off and that their minds were wandering. The study also showed that when these patients were asked to relax, their brains were more active than healthy women. The researchers hope these findings can help healthcare providers measure the effect that chemotherapy has on the patients' brains.  

Current tests to assess the cognitive ability of chemotherapy patients have been developed for other cognitive disorders, such as Alzheimer’s or brain injury. These have proven to be ineffective, because the cancer survivors have often been able to complete these tests without a problem, only to suffer memory loss or fogginess when they return home, adding to their distress.   

“Physicians now recognize that the effects of cancer treatment persist long after it’s over and these effects can really impact a person’s life,” said Kristin Campbell, lead researcher. “These findings could offer a new way to test for chemo brain in patients and to monitor if they are getting better over time.”