Regular aerobic exercise improves blood flow to the brain, which should help keep seniors sharper as they age, a new trial has revealed.
At least a half-hour of power walking or jogging four to five times a week promoted better blood flow in and out of the brain among a small group of older adults, said study co-author Rong Zhang. He directs the cerebrovascular laboratory at the Institute for Exercise and Environmental Medicine, a collaboration between UT Southwestern and Texas Health Presbyterian Hospital Dallas.
"The intensity was like if you're rushing to a meeting where you are 10 minutes late," Zhang said. "You're brisk walking, and you feel a shortness of breath."
The brain requires about 20% of the body's total blood flow to maintain its function as an organ, he said.
But as people age, blood starts to flow less freely in and out of the brain, a condition called cerebrovascular impedence.
Less blood flow means the brain is receiving lower levels of oxygen and nutrients, Zhang said.
It also means that toxins could build up in the brain, since reduced blood flow is less able to carry away waste products generated by the brain's high metabolism.
To see whether regular exercise could help people maintain healthy blood flow to their brain, Zhang and his colleagues recruited 72 people between the ages of 60 and 80 to take part in a yearlong experiment.
Half were randomly assigned to an aerobic exercise group, while the rest were placed in a control group that performed stretching and toning activities.
The aerobics group started with three half-hour exercise sessions a week, and gradually increased to four or five sessions that could run as long as 40 minutes.
After a year of exercise, researchers performed brain scans and arterial tests to see how well blood was flowing in and out of the participants' brains.
The aerobics group showed a significant improvement in brain blood flow by the end of the year, but the stretching and toning group did not.
This sort of improvement in blood flow should lead to better brain health, said Dr. Donn Dexter, a neurologist with the Mayo Clinic in Eau Claire, Wisc., and a fellow of the American Academy of Neurology.
"The data on exercise improving cognition is pretty solid," Dexter said. "I have not seen this tack taken before. It's interesting that they're looking at exercise as a way to improve vascular health inside the brain. This adds more fuel to that hypothesis that exercise improves brain health."
Current guidelines recommend adults get at least 150 minutes a week of moderate-intensity exercise, Dexter and Zhang said.
"It's hard to remember 150 minutes a week. Keeping track of that might be difficult," Dexter said. "So what I tell them is do 30 minutes a day, because 30 minutes a day will get you that 150 minutes a week, even if you miss a day or two."
This study shows that people can receive the benefits of exercise at any age, given that the participants were at least 60, Zhang said.
"Exercise should be a habit for your whole life. It's never too late," he said. "The research out there suggests what is good for your heart is good for your brain. That's a message we need people to understand."
At the same time, people shouldn't feel they have to overdo it, Zhang added.
"I haven't seen any evidence suggesting that if you go to the extreme, like people training for a marathon, you will receive more benefits compared with the program we have recommended," he said.
The clinical trial report was recently published in the Journal of Applied Physiology.