If you’re noticing a growing number of senior moments — where did I put those keys? — you might consider taking a walk.
New research published in the Proceedings of the National Academy of Sciences (PNAS) confirms the brain benefits of physical activity for older adults, but this time with the added evidence that walking can actually increase the volume of certain parts of the brain involved in memory.
Until recently, researchers thought that new nerves did not sprout in already developed adult brains, while with age worn out neurons slowly die off. But once imaging studies proved them wrong, scientists documented two areas where nerve growth seemed to be the most active — the olfactory bulb (involved in smell) and a portion of the hippocampus, which is responsible for regulating learning and memory. (More on TIME.com: Want to Live Longer? Start Walking–Quickly)
In the PNAS study, scientists started with 120 elderly volunteers who were relatively inactive but did not have dementia. Half were randomly assigned to begin walking 40 minutes a day, three days a week for a year while the remainder only stretched and performed toning exercises for the same time period. After 12 months, the group that walked showed an average 2% growth in the hippocampus compared with when they began, while the control groups suffered a more than 1% shrinkage in the same region compared with when the study started.
“If you estimate the change at an individual level,” says study co-author Arthur Kramer of the University of Illinois, “a yearlong exercise program can turn back the clock about two years with respect to the volume of the hippocampus.” (More on TIME.com: Study Shows Walking is Brain Exercise, Too)
It’s strong evidence that physical activity can not only get blood circulating and improve bone and muscle mass, but may also trigger new neurons to grow, giving aging brains a cushion of memory connections that may make a difference in everyday life.
How is the exercise helping? Kramer isn’t sure yet, but thinks that the improved blood flow can boost connections between neurons and also ferry important nutrients and growth signals that nerve cells need to thrive. Exercise also increases levels of certain hormones and brain chemicals that may provide a rich environment for newly formed nerves.
“Exercise is medicine, without the side effects and the astronomical costs,” he says. That may be true, but it’s still a bitter pill to swallow for most of us, who prefer to remain sedentary. But maybe the promise of a sharper mind may finally get more of us off the couch.
More on TIME.com:
Anxious Kids? Let Them Walk to School
Study: Exercise Can Protect People at High Risk of Alzheimer’s
Want to Keep the Pounds Off? The Trick is Consistent Exercise