New York (AP): Getting a lot of exercise may help slow brain shrinkage in people with early Alzheimer's disease, a preliminary study suggests.

Analysis found that participants who were more physically fit had less brain shrinkage than less-fit participants. However, they didn't do significantly better on tests for mental performance.

That was a surprise, but maybe the study had too few patients to make an effect show up in the statistical analysis, said Dr Jeffrey Burns, one of the study's authors.

He also stressed that the work is only a starting point for exploring whether exercise and physical fitness can slow the progression of Alzheimer's. The study can't prove an effect because the participants were evaluated only once rather than repeatedly over time, he said.

While brains shrink with normal aging, the rate is doubled in people with Alzheimer's, he said.