The study found that seniors who got moderate to intense exercise retained more of their mental skills over the next five years, versus older adults who got light exercise or none at all.
On average, those less-active seniors showed an extra 10 years of "brain aging," the researchers said.
The findings do not prove that exercise itself slows brain aging, cautioned senior researcher Dr. Clinton Wright, a neurologist at the University of Miami Miller School of Medicine.
It's possible, he said, that there are other reasons why active older adults stayed mentally sharper.
The researchers accounted for some of those other explanations -- including people's education levels, smoking habits and health conditions such as high blood pressure and diabetes.
And exercise levels were still connected to the participants' performance on tests of memory and "processing speed" -- the ability to digest a bit of new information, then respond to it.
Plus, Wright said, it's plausible that exercise would affect those mental skills. Other research has shown that physical activity boosts blood flow to the brain, and may enhance the connections among brain cells, for example.
