Breast cancer survivors often complain of thinking and memory problems that occur during and after undergoing chemotherapy. The effects are called chemo brain or chemo fog, and they are real, say researchers from the University of Illinois, who found long-lasting cognitive impairments in mice given chemotherapy.

"Cancer survival rates have increased substantially and continue to improve due to both earlier detection and better medical treatments," said the study's lead author Catarina Rendeiro, a postdoctoral scholar at the Beckman Institute for Advanced Science and Technology. But chemo brain is a significant complaint in survivors, and many questioned whether the effects lasted for only a short length of time or were long-lasting.

First, the study needed to confirm that chemo brain was real. The researchers used female mice bred to mimic post-menopausal women, the group most affected by breast cancer. They found that mice which had received chemotherapy performed tasks more slowly and were slower to learn new tasks when compared with a control group.

They also found that the chemotherapy group had 26 percent fewer surviving hippocampal neurons created during the chemotherapy treatment and generated 14 percent fewer hippocampal neurons in the three months following chemotherapy. Three months for a mouse corresponds to about ten human years.

Together, the results showed long-term detriments to both the brain and behavior of the chemotherapy-treated mice.

The results were published in the journal Behavioural Brain Research.

What causes chemo brain? No one is sure. Possible causes include the cancer itself and drugs such as steroids used in treatment and anesthesia used in surgery.

According to cancer.org, symptoms of chemo brain include:

• Trouble remembering names and dates
• Problems concentrating
• Taking longer to finish things
• Trouble remembering common words