Brisk walking improves brain health and thinking in aging people with memory impairments.

In a yearlong study of mild cognitive impairment and exercise, middle-aged and older people with early signs of memory loss raised their cognitive scores after they started walking frequently. Regular exercise also amplified the healthy flow of blood to their brains.

The changes in their brains and minds were subtle but consequential, the study concludes, and could have implications not just for those with serious memory problems, but for anyone whose memories are starting to fade with age.

Most of us, as we get older, find that our ability to remember and think dulls a bit. This is considered normal, if annoying. But if the memory loss intensifies, it can become mild cognitive impairment, a medical condition that is not dementia, but people with the condition are at heightened risk of developing Alzheimer's disease later.

Scientists have not pinpointed the underlying causes of mild cognitive impairment, but there is some evidence that changes in blood flow to the brain can contribute. Blood carries oxygen and nutrients to brain cells, and if that stream sputters, so can the vitality of neurons.

Unfortunately, many people experience declines in the flow of blood to their brains with age, when their arteries stiffen and hearts weaken. But the good news is that exercise can increase brain blood flow.

In a 2013 neurological study, the brains of physically active older men showed much better blood saturation than those of sedentary men. The greater brain blood flow in people who exercise also is associated with better scores on tests of memory and thinking than among sedentary people.

Details of the report

For the new study, which was published in the Journal of Alzheimer's disease, researchers at the University of Texas Southwestern Medical Center in Dallas and other institutions asked a group of 70 sedentary men and women, ages 55 or older and diagnosed with mild cognitive impairment, to start moving more.

They first brought everyone into a lab and tested their current health, cognitive function and aerobic fitness. Then, using advanced ultrasounds, they measured the stiffness of their carotid artery, which carries blood to the brain, and the amount of blood flowing to and through their brains.

Finally, they divided the volunteers into two groups. One began a program of light stretching and toning exercises, to serve as an active control group. The others started to exercise aerobically, mostly by walking on treadmills at the lab twice a week, and then, after a few weeks, outside five days a week. The exercisers were asked to keep their exertions brisk, so that their heart rates and breathing rose noticeably. The control group kept their heart rates low.

After a year, the volunteers returned to the lab for a repeat of the original tests. To no one's surprise, the exercise group was more fit, with higher aerobic capacity, while the stretchers' endurance had not budged. The aerobic exercise group also showed much less stiffness in their carotid arteries and, in consequence, greater blood flow to and throughout their brains.

Perhaps most important, they also performed better than the stretch-and-tone group on some of the tests of executive function, which are thinking skills involved in planning and decisionmaking. These tend to be among the abilities that decline earliest in dementia.

The researchers believe that over a longer period, brisk walking would result in greater cognitive gains and less memory decline than gentle stretching, said Rong Zhang, a neurology professor at UT Southwestern Medical Center, who oversaw the new study.

"It probably takes more time" than a year for the improved brain blood flow to translate into improved cognition, he said. He and other researchers are planning larger, longer-lasting studies to test that idea, he said. They hope, too, to investigate how more — or fewer — sessions of exercise each week might aid the brain.

For now, though, he believes the group's findings serve as a useful reminder that moving changes minds. "Park farther away" when you shop or commute, he said. "Take the stairs," and try to get your heart rate up when you exercise. Doing so, he said, might help to protect your lifelong ability to remember and think.