• NEWS
• 03 November 2025

A modest increase in physical activity can delay cognitive decline by three years — or more.

By

• Mariana Lenharo0

1. Mariana Lenharo

Mariana Lenharo is a news reporter for Nature based in New York City.

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 finds1.

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 very encouraging takeaway is that even a little bit of exercise seems to help,” says Wai-Ying Wendy Yau, a physician-scientist specializing in memory disorders at Harvard Medical School in Boston, Massachusetts, and a co-author of the study, which was published on 3 November in Nature Medicine. The research indicates that people don’t need to take 10,000 steps a day, a goal that is often touted but might be hard for some older individuals to attain, she says.

Steps towards prevention

The research team ran regular checks on 296 people participating in the Harvard Aging Brain Study, a programme that is investigating the early stages of Alzheimer’s. None of them had signs of cognitive impairment at the beginning of the study. Over a period of up to 14 years, the team periodically assessed the participants — whose ages ranged from 50 to 90 — using cognitive tests and brain scans. Participants were also asked to wear pedometers to measure how many steps they took each day.

The brains of people at a higher risk of Alzheimer’s disease usually show an abnormal build-up of two proteins: amyloid-β and tau. Although the relationship between the two proteins is not fully understood, amyloid-β levels begin to increase first, followed by tau levels. Cognitive decline seems to be more closely tied to the accumulation of tau.

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.

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doi: https://doi.org/10.1038/d41586-025-03596-2

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