It's never too late to start exercising, especially when it comes to brain fitness.
Neurologists have long known that our brains get slightly smaller as we grow older and that this shrinkage is associated with a gradual decline in certain mental functions. Previous research has demonstrated that regular exercise can slow the pace of shrinkage and help protect memories and preserve the ability to learn new things.
Now, a new study suggests that even starting an exercise program later in life can undo some of the brain shrinkage in seniors who've spent years as couch potatoes.
"Our results show we can reverse the atrophy that was already taking place," said the lead researcher, Kirk Erickson of the University of Pittsburgh.
For the study, they recruited 120 healthy but sedentary volunteers, ranging in age from 60 to 80. (None had been diagnosed with dementia or were suspected of having Alzheimer's disease.)
Half of the seniors were given an aerobic exercise regimen of walking around a track for 40 minutes a day, three days a week. Aerobic exercise is designed to increase the heart rate for an extended period.
The other half served as a control group. They were told to do stretching and toning exercises - activities that would barely budge their heart rates.
Each participant underwent a series of MRI scans to measure changes in the size of the hippocampus, the brain structure involved in all forms of memory formation.
The findings, published in the Proceedings of the National Academy of Sciences, revealed a dramatic difference in the two groups after one year. The walkers experienced increases in volume of the left and right hippocampus by 2.12 and 1.97 per cent respectively. The same regions of the brain in those who did stretching decreased by 1.40 and 1.43 per cent, respectively, which amounts to the normal expected shrinkage.
"You can think of the increase in volume of the hippocampus as turning back the clock by about two years," explained the senior author of the study, Art Kramer of the University of Illinois.
Furthermore, the bigger brains seemed to work better. Tests conducted over the course of the study showed that those in the aerobic exercise group demonstrated improved memory function, compared with their performance measured at the beginning of the trial.
The researchers are continuing to observe the volunteers. Dr. Erickson expects that hippocampus expansion of the walkers "will eventually slow down and stop" because the brain generally shrinks with age. But when atrophy does becomes apparent once more, the rate of shrinkage will likely be slowed if they keep exercising regularly.
Dr. Kramer stressed that it doesn't take a complex or particularly strenuous exercise program to produce meaningful results. "All you need is a pair of walking shoes and a place to walk," he added.