Physical exercise is better for the brain than mind games suggests a new study.
Researchers at the University of Edinburgh found that working out slowed signs of dementia better than doing crossword puzzles.
BBC said that the study took brain scans of 638 retired people.
Those who reported being the most physically active showed less brain shrinkage, a key sign of dementia, than those who did not exercise.
"People in their seventies who participated in more physical exercise, including walking several times a week, had less brain shrinkage and other signs of aging in the brain than those who were less physically active," said study author Alan J. Gow, reported LiveScience.
"On the other hand, our study showed no real benefit to participating in mentally and socially stimulating activities on brain size, as seen on MRI scans, over the three-year time frame."
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Researchers stressed that the exercise did not have to be intense.
Indeed, just a walk a few times per week was enough to stave off some of the effects of brain ageing.
Exercise increases blood flow to the brain, which delivers oxygen to brain cells.
Yet, the study also found that doing mentally-challenging activities like puzzles had no real benefit for brain size.
"This study links physical exercise to fewer signs of ageing in the brain, suggesting that it may be a way of protecting our cognitive health," Simon Ridley, head of research at Alzheimer's Research UK, told BBC.
"While we can't say that exercise is the causal factor in this study, we do know that exercise in middle age can lower the risk of dementia later in life."
The study was published in the journal Neurology.