When it comes to preventing Alzheimer’s disease, every step counts. For older people whose brains have begun to show molecular signs of the disease, but who have yet to display any cognitive symptoms, taking as few as 3,000 to 5,000 steps per day can help to stave off mental decline, a study finds.

That level of activity slows cognitive decline by 3 years, on average, the results show. And in similar individuals who walk further, taking 5,000 to 7,500 steps per day, decline slows by an average of 7 years. The work also offers hints to how exercise alters the brain to offer this protection.

The benefits of taking 3,000 to 7,500 steps per day were apparent only for participants with high baseline levels of amyloid-β in their brains. Their mental decline was slowed — by 3 to 7 years — compared with participants who were sedentary. The researchers didn’t see any further slowing of mental decline in participants who took more than 7,500 steps a day… Brain scans revealed that higher levels of physical activity specifically slowed the build-up of tau; amyloid-β accumulation continued on its upwards trajectory… Among participants with low baseline levels of amyloid-β — and therefore a low risk of Alzheimer’s disease — exercise levels had no effect on cognitive trajectory.

The associated study on Nature Medicine which is open access: https://www.nature.com/articles/s41591-025-03955-6