For some women, the end of breast cancer treatment is supposed to mark the beginning of getting back to normal. But what if your brain doesn't get the memo? "Chemo brain" is the term often used to encapsulate the problems women can have concentrating, recalling things or keeping up with everyday tasks that can linger long after treatment ends.

Now, new research suggests that exercise may help, and the benefits may extend down to the cellular level.

"What is particularly striking about these findings is that the effects of exercise were measurable both at the molecular level and in cognitive performance.”

The research comes from two companion studies involving breast cancer survivors who had completed active treatment. Both grew out of a randomized clinical trial conducted by researchers at the University of California, San Diego's Moores Cancer Center.

The main study included over 250 breast cancer survivors who reported both cognitive difficulties and low levels of physical activity. Participants were randomly assigned to one of two groups. One received a remotely delivered exercise program; the other participated in a health-and-wellness program that provided regular contact with a health coach, but did not include exercise coaching.

Those in the exercise group wore fitness trackers and received individualized coaching designed to help them work toward 150 minutes of moderate to vigorous physical activity a week.

Women in the exercise group showed greater improvements in concentration at both six and 12 months.

The results:
  • After a year, the exercise group had increased its physical activity more than the comparison group.
  • Both groups improved on measures of cognitive function.
  • The researchers found no significant difference between the groups in the study's two primary outcomes: processing speed and self-reported cognition.
But there was a difference in attention. Women in the exercise group showed greater improvements in concentration at both six and 12 months. They also showed more improvement in memory at six months, although that advantage had disappeared by 12 months. There was no significant difference between the groups in executive function.

Sheri Hartman, a professor at UC San Diego's UC Herbert Wertheim School of Public Health and Human Longevity Science and a member of the Moores Cancer Center, was the lead author of the study on exercise's effects on survivors' cognition. "Attention is central to our everyday activities," Hartman said in a University of California San Diego news release. "It helps us follow conversations, absorb information and complete tasks without making errors, so the sustained improvements we saw in this trial is particularly encouraging."

The second study examined something considerably more microscopic: biological aging. Researchers selected a subset of 124 participants who provided blood samples at the beginning of the study and again after six and 12 months.

They studied DNA methylation — patterns of chemical changes that influence how genes function — to calculate what is known as epigenetic age.

Unlike chronological age, which simply counts the years since you were born, epigenetic age is an estimate based on biological markers associated with aging.

In this study, the participants' biological clocks were already running ahead of their birthdays. The group's epigenetic ages were, on average, about 8.7 years older than their chronological ages. After 12 months, however, the pace of epigenetic aging was considerably slower in the exercise group. The researchers estimated roughly one month of epigenetic aging in that group compared with nearly 10 months in the group who had contact with the same health coach as those in the exercise group, but who only received information and emails on a variety of wellness topics from the coach.

At the start, women's biological or epigenetic ages were, on average, about 8.7 years older than their chronological ages. After 12 months, however, the pace of epigenetic aging was considerably slower in the exercise group.

"What is particularly striking about these findings is that the effects of exercise were measurable both at the molecular level and in cognitive performance,” co-senior author of the companion study, Paula Desplats, a professor of neurology at the Ohio State University and an adjunct professor of neuroscience at the UC San Diego School of Medicine, said in a news release.

People whose epigenetic aging progressed more quickly tended to show less improvement in attention and worse self-reported cognition the study found. That is an association; the relationship does not prove that slowing biological aging causes better thinking.

The findings are encouraging, but though they show a connection, they don't prove that exercise can prevent or reverse cognitive problems after breast cancer treatment. Larger studies are needed to determine how much exercise is necessary, who is most likely to benefit and whether the cognitive improvements can last.

Still, the study offers breast cancer survivors an intriguing possibility. The physical activity that helps keep the body strong may also help the brain and influence some of the biological processes associated with aging.

Both studies are published in the Journal of the National Cancer Institute.