Brain health has been a hot topic lately—especially now that an estimated one in 10 Americans over 65 are living with Alzheimer's in 2017. In the past, studies have shown that exercise can keep your brain healthy as you age, and a new study published in the Journal of Alzheimer's Disease found even more evidence to support those findings. 

In the study from UT Southwestern, researchers had older people with a high risk of developing Alzheimer's take memory and other mental tests to measure their brain function, and used their VO2 max ratings to gauge their fitness levels. (Using VO2 max ratings sets the study apart from past research, which relied on people to self-report their own fitness levels.)

Participants' brains were also scanned to see how well their white matter—the bundles of nerves in the brain that affect learning, brain function, and communication between different parts of the brain—was functioning. Of the patients, who all had early signs of memory loss or mild cognitive impairment, the less physically fit people tended to have weaker white matter, which correlates with lower brain function.

"This research supports the hypothesis that improving people's fitness may improve their brain health and slow down the aging process," said study author Kan Ding, M.D., a neurologist from UT Southwestern's Peter O'Donnell Jr. Brain Institute.

While the findings are promising, there's still a lot of research to do when it comes to the effects that regular exercise has on the brain. It's not clear how fit someone needs to be to significantly reduce the risk of dementia, or how late is too late when it comes to starting a program when someone already experiences symptoms of cognitive impairment. 

"Evidence suggests that what is bad for your heart is bad for your brain," said study author Rong Zhang, Ph.D. "We need studies like this to find out how the two are intertwined and hopefully find the right formula to help prevent Alzheimer's disease."