The short answer: in large observational studies, people who walk more have a lower risk of dementia, and in one UK study the risk was about half as high at roughly 9,800 steps a day. Walking also changes the brain in some trials. But the best long trial of an activity program in older adults did not prevent cognitive decline, so we can't say that walking more will prevent dementia, only that it is linked with lower risk and has other benefits that matter for the brain.
The step-count study
The most detailed data come from a 2022 study in JAMA Neurology (del Pozo Cruz, Ahmadi, Naismith and Stamatakis). It followed 78,430 UK Biobank participants aged 40 to 79, with an average age of 61, who wore a wrist accelerometer for a week between 2013 and 2015. Over a median of 6.9 years, 866 developed dementia. More steps went with lower risk, with the largest relative gains at the low end, and more intense steps mattered too.
| Measure in the UK Biobank study | Dementia risk compared with the least active (hazard ratio) |
|---|---|
| About 3,800 steps a day (the "minimal dose," half the maximum benefit) | 25% lower (0.75) |
| About 9,800 steps a day (the "optimal dose," the largest reduction seen) | 51% lower (0.49) |
| About 6,300 purposeful steps a day (taken at 40 or more steps a minute) | 57% lower (0.43) |
| Fastest 30 minutes of the day averaging 112 steps a minute | 62% lower (0.38) |
An editorial in the same journal asked whether 112 might be "the new 10,000." The intensity finding is interesting because 112 steps a minute is a purposeful, fairly brisk walk (the CADENCE-Adults research puts moderate intensity at about 100 steps a minute; see power walking). The limits are important, though. Activity was measured once, for a week. People in the early, undiagnosed stages of dementia may already move less, which can make walking look more protective than it is; and people who walk more tend to differ in health, income and education. A 2025 review of step counts in The Lancet Public Health (Ding and colleagues) also found dementia among the outcomes linked with higher daily steps; see how many steps you need.
What trials show
A 2011 randomised trial in PNAS (Erickson and colleagues) assigned 120 older adults without dementia to a year of moderate walking, 40 minutes three times a week, or to stretching and toning. The walking group's anterior hippocampus, a region important for memory that typically shrinks 1 to 2% a year in later life, grew by about 2%, while the stretching group's shrank by about 1.4%. Spatial memory improved in both groups, though, which critics pointed out in a published letter, so the trial shows a change in brain structure more clearly than a memory benefit.
The largest test of prevention is the LIFE trial (Sink and colleagues, JAMA, 2015). It randomised 1,635 sedentary adults aged 70 to 89, at risk of mobility problems, to a two-year moderate physical activity program, built mainly around walking with strength, flexibility and balance work, or to a health education program. At two years, cognitive test scores did not differ, and mild cognitive impairment or dementia occurred in 13.2% of the activity group and 12.1% of the education group, a difference that wasn't significant. A later analysis found the activity program reduced "cognitive frailty," a combination of physical frailty and cognitive impairment. So in older, sedentary adults, two years of a walking-based program did not measurably slow cognitive decline.
How the two fit together
The studies don't necessarily contradict each other. Dementia develops over decades, and a two-year trial in people in their 70s and 80s may start too late or run too briefly to show an effect, while observational studies can overstate benefits for the reasons above. The 2024 Lancet Commission on dementia counts physical inactivity among 14 modifiable risk factors, alongside others such as high blood pressure and diabetes, and walking has stronger trial evidence for those: it lowers blood pressure modestly (walking and heart health) and improves glucose control (walking and blood sugar). That indirect route is a reasonable reason to walk, even if direct prevention isn't proven.
What this means in practice
This part is our reading of the evidence. Regular walking is worth doing for many reasons, and the dementia findings are one more, without being a guarantee. The study data suggest that both the amount and the pace matter, so some brisk walking alongside your daily steps is sensible; Japanese interval walking is one structured way to add it. Walking is not a treatment for memory problems that have already started. If you or someone close to you is noticing changes in memory or thinking, talk to a doctor. For the mood side of walking, see walking and mental health.
Sources
- del Pozo Cruz B, Ahmadi M, Naismith SL, Stamatakis E. Association of daily step count and intensity with incident dementia in 78,430 adults living in the UK. JAMA Neurology. 2022;79(10):1059-1063. researchgate.net
- Erickson KI, Voss MW, Prakash RS, et al. Exercise training increases size of hippocampus and improves memory. PNAS. 2011;108(7):3017-3022. pnas.org
- Failure to demonstrate that memory improvement is due either to aerobic exercise or increased hippocampal volume (letter). PNAS. 2011;108(18):E89. pnas.org
- Sink KM, Espeland MA, Castro CM, et al. Effect of a 24-month physical activity intervention vs health education on cognitive outcomes in sedentary older adults: the LIFE randomized trial. JAMA. 2015;314(8):781-790. PubMed
- Effect of 24-month physical activity on cognitive frailty and the role of inflammation: the LIFE randomized clinical trial. BMC Medicine. 2018. PMC
- Ding D, Nguyen B, Nau T, et al. Daily steps and health outcomes in adults: a systematic review and dose-response meta-analysis. The Lancet Public Health. 2025;10(8):e668-e681. thelancet.com
- Association between physical activity levels, sedentary time, and mild cognitive impairment in older adults (citing the 2024 Lancet Commission on dementia). Frontiers in Public Health. 2026. frontiersin.org
How we checked: the figures come from published abstracts, journal pages and summaries, checked on October 13, 2026. The Lancet Commission is cited through a 2026 paper that summarises it, not the report itself, and we have not given a figure for how many cases could be prevented. The description of the LIFE program as mainly walking-based reflects the trial's design as reported in summaries. This article is for informational purposes and does not replace medical advice; if you are worried about memory or thinking, talk to a doctor. This is general information, not medical advice.