Gretchen Reynolds
Regular exercise during midlife makes brains functionally younger.
That’s the bracing conclusion of a new study of 130 inactive men and women, most in their 40s. Some began a simple, aerobic exercise program. Others didn’t.
At the end of a year, the exercisers’ brains appeared more youthful on scans than they had been at the start. The brains of the others looked slightly older than before.
The results “are telling us that the brain is modifiable, and that exercise is a great way to modify it,” says Kirk I. Erickson, director of translational neuroscience at the AdventHealth Research Institute in Orlando and senior author of the study.
They also indicate that midlife may be “an important inflection point” for brain health, Erickson continues. Exercise between the ages of about 35 to 55 might “change the trajectory of brain ageing” for years to come.
“This is important work,” says Jennifer Heisz, director of the NeuroFit Lab at McMaster University in Ontario, Canada. She studies exercise neuroscience but was not involved with the study.
The findings raise questions, though, about which workouts might be best, how exercise actually slows or reverses brain age and whether it’s ever too late to turn back the clock on your brain.
Exercise remodels brains
The idea that exercise influences brain health is almost indisputable now. Decades ago, researchers discovered that aerobic exercise, such as running, doubled or tripled the creation of brain cells in rodents and presumably in people. Exercise also amplified the production of neurochemicals that promote new blood vessels and cellular connections throughout the brain.
And in a seminal exercise neuroscience study from 2011, Erickson and his colleagues found that a year-long program of brisk walking increased the volume of the hippocampus in older volunteers. The hippocampus is an area of the brain essential to memory formation that usually shrinks with age. It grew in the older men and women who started to exercise.
Much of this past research focused on older people, understandably, because they tend to be the ones whose brains and thinking falter and fade.
But recently Erickson began wondering about midlife. Are our brains ageing then in ways that influence our cognitive resilience or decline later? Can we change that process? Would exercise matter?
Or, in simpler terms, could midlife exercise affect the biological age of people’s brains?
What is biological age?
Biological age refers to our bodies’ functioning, or how well it works compared with the bodies of other people who share our birth date. Your biological age can be higher or lower than your chronological age, depending on how healthy you are, and so can the biological age of each of your organs (and probably each of your cells).
Your brain, for instance, is believed to have a biological age – known, mundanely, as your brain age – that can be assessed in various ways. One of the simplest is a brain scan that documents its structure, including levels of white and grey matter, lesions, blood vessels, etc.
Machine learning algorithms then can compare your brain’s structure to that seen in tens of thousands of scans of other people of all ages to estimate your brain’s biological age.
In studies, a low brain age, especially one lower than your actual age, is associated with better cognitive health in old age and less risk of dementia or other conditions caused by neurodegeneration.
But it hasn’t been clear how fitness and exercise affect brain age, especially in midlife adults whose brains presumably are about as healthy as they’ll ever be.
How exercise affects brain age
So Erickson and his colleagues recruited 130 men and women, age 26 to 58, who rarely, if ever, exercised. The researchers checked everyone’s aerobic fitness, blood pressure, body mass index and other measures of health, and scanned their brains with magnetic resonance imaging, to determine brain age.
Then half of the volunteers started a supervised aerobic exercise program, showing up at a university lab to work out twice a week for about an hour, using treadmills, bicycles or other equipment. The workouts were challenging but not punishing, mostly brisk walking or jogging. People also worked out at home several times a week, until they had completed at least 150 minutes a week of exercise.
The control group continued with its normal routines.
After a year, everyone returned to the lab for a second round of health tests and brain scans.
As expected, the exercisers were fitter than before and, in general, fitter than the control group.
More surprising, their brains looked different than they had at the start, unlike the control group’s.
They looked younger.
Seven months younger
On average, the exercisers had reduced their brain age by the equivalent of about seven months.
That decline isn’t large, Erickson says, but “over time, the cumulative change in brain age” with exercise “could add up to quite a few years’ reduction down the road”.
Meanwhile, the brains of people in the control group generally looked older (which makes sense, because a year had passed).
Interestingly, the scientists found no correlation between changes in fitness, blood pressure, body weight or other health markers and changes in brain age.
“This suggests something else” drove the relationship between physical activity and lower brain age, Erickson says, such as altered inflammation, insulin sensitivity or stress hormone levels after exercise.
His group plans to focus on those health markers in future publications and experiments, he says.
There also are questions about whether brain age is the best gauge of brain health, Heisz says. “It doesn’t tell us which specific brain regions changed, whether cognition improved, or whether dementia risk was actually reduced,” she says.
Erickson agrees and says he and his colleagues will look at individual brain regions such as the hippocampus in upcoming studies. They’ll also track the effects of brain-age changes on thinking skills and memory. And they’re hoping to assess how much and which types of exercise prompt the greatest reductions in brain age, as well as whether those reductions are similar in elderly people who start to exercise.
But for now, Erickson says, this study is further confirmation that, “outside of pharmaceutical approaches,” regular exercise seems to be “the most robust” way to keep your brain youthful and strong, whatever your age.
Washington Post
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