See more of the story

For some people with early-stage Alzheimer’s disease, frequent, brisk walks may help to bolster physical abilities and slow memory loss, according to one of the first studies of physical activity as an experimental treatment for dementia.

But the study’s results, while encouraging, showed that improvements were modest and not universal, raising questions about just how and why exercise helps some people with dementia and not others.

There are currently no reliable treatments for the disease. But past studies of healthy elderly people have found relationships between regular exercise and improved memories. Physically active older people are, for instance, significantly less likely than those who are sedentary to develop mild cognitive impairment, a frequent precursor to Alzheimer’s disease.

Physically fit older people also tend to have more volume in their brain’s hippocampus than do sedentary people of the same age, brain scans show. The hippocampus is the portion of the brain most intimately linked with memory function.

But most of this research has examined whether exercise might prevent Alzheimer’s disease.

Little has been known about whether it might change the trajectory of the disease in people who already have the condition.

So for the new study, published in PLoS One, researchers at the University of Kansas decided to work directly with people who had previously been given a diagnosis of Alzheimer’s disease. Because the disease can affect coordination as it progresses, the researchers focused on men and women in its early stages.

The volunteers were divided into two groups.

One began a supervised walking program that was supposed to raise their physical fitness. They walked progressively longer and faster over the course of several weeks, until they were briskly walking for at least 150 minutes each week.

The second group, serving as a control, began stretching and toning classes. These sessions were designed to be light exercise that would not increase aerobic endurance but would mimic the time commitment and social interactions of the walkers.

Both groups continued their regimens for six months and then returned to the lab for repeat testing.

Encouragingly, many showed gains in physical functioning, particularly among the walkers. Almost all of them had significantly improved their scores on the tests of everyday physical skills.

But the effects of the experiment on thinking and memory were more mixed.

Most of those in the control group were now slightly less able to think clearly and remember than they had been six months before, new tests showed. The toning had not slowed the progression of their disease much, if at all.

Similarly, many of the walkers performed no better and some scored worse on the cognitive tests than at the start.

But some of the walkers were thinking and remembering much better, according to their cognitive tests. These volunteers also generally showed slight increases in the size of their brain’s hippocampus.