WEDNESDAY, April 18 (HealthDay News) -- New research suggests that elderly people who move around more -- even gardening or puttering around the house -- are less likely to develop Alzheimer's disease than more sedentary seniors.

The study doesn't confirm that being active lowers the risk of Alzheimer's, an age-related degenerative brain disease. It's possible that another factor explains the link; perhaps the very early stages of Alzheimer's cause people to slow down.

Still, the findings suggest that "an active lifestyle may be good for you. Even if you can't exercise, increasing all kinds of movements may be beneficial in the long term," said study lead author Dr. Aron Buchman, an associate professor of neurological sciences at Rush University Medical Center, in Chicago.

Previous research has pointed to a possible link between exercise and healthy brains. "Cardiovascular conditioning gets our hearts to pump oxygen and nutrients to our brain cells, which helps them communicate more effectively and protects neural health," said Dr. Gary Small, a brain researcher and director of the Longevity Center at the University of California, Los Angeles. He was not involved with the study.

By 2030, it is estimated that the number of Americans older than 65 will double to 80 million. Given this surge, the authors say the new study has significant public health implications.

In the study, researchers wanted to see if simply moving around -- not necessarily working up a sweat -- might make a difference.

The study looked at 716 people without dementia -- average age 82, including 602 women -- whose activity was tracked for as many as 10 days with the help of a device that measures movement. The device, called an actigraph, picks up traditional forms of exercise, such as walking and swimming, but also monitors when people fidget or move around the house, said study lead author Buchman.

"It's like a wristwatch and is pretty nonobtrusive," he said. "They wear it 24 hours a day."

The researchers then watched to see what happened to the participants. Over an average of almost four years, 71 developed signs of Alzheimer's disease. The researchers analyzed their statistics to see if the risk of the illness was higher or lower depending on the activity levels of the participants back when they wore the devices.

Those among the 10 percent of participants who were most active had an 8 percent likelihood of developing signs of Alzheimer's over the time period in which they were followed. The risk jumped to 18 percent among the 10 percent of participants who were the least active.

Buchman acknowledged that it's impossible to know which comes first: little activity or brain problems. "The whole issue of whether there's a causal relationship between physical activity and cognition is one that needs to be sorted out," he said.

One challenge to understanding the link between exercise and the brain is that an ideal study would need to assign some people to be more active and others to be less active. And, according to Dr. William Jagust, a professor of neuroscience at the Helen Wills Neuroscience Institute at the University of California, Berkeley, then they'd need to be followed for a long time to confirm whether activity (or lack of it) makes a difference.

The study appears online April 18 and in the April 24 print issue of Neurology.

The authors acknowledged some study limitations. Because the study volunteers included so many more women than men, the results might not apply to the population at large, they said. Also, the devices didn't distinguish among the different activities performed.

More information

For more about Alzheimer's disease, see the U.S. National Library of Medicine.