November 12, 2025
Walking just a few thousand steps a day may slow the progression of Alzheimer’s among older adults at heightened risk of developing the disease, according to a new report. The study found that moderate amounts of physical activity were associated with slower rates of cognitive decline in healthy older men and women who had elevated brain levels of beta-amyloid, a hallmark of Alzheimer’s. High levels of the toxic protein are linked to an increased risk of Alzheimer’s.
For the study, researchers looked at health data from 296 older men and women who were part of the Harvard Aging Brain Study, an ongoing, long-term study that looks at changes in the brain and how they correlate with declines in cognitive skills. They ranged in age from 50 to 90. None of them had serious memory problems at the start of the study period, though some had elevated brain levels of beta-amyloid, as detected by brain PET scans.
At the start of the study period, participants wore health-tracking wrist bands to detect how many daily steps they took over an average week. They were then followed for up to 14 years, receiving annual tests of thinking and memory skills as well as tests to measure functional skills like getting dressed and the ability to carry out a range of day-to-day activities. More than half also got regular PET scans to track changes in beta-amyloid and tau levels in the brain.
The researchers found that in those adults who had increased levels of beta-amyloid in the brain at the start of the study, higher step counts were tied to slower rates of cognitive decline. In those who walked 3,000 to 5,000 steps a day, declines in thinking and memory skills and the ability to carry out day-to-day tasks were delayed on average by three years. Those who walked 5,000 to 7,500 steps a day delayed cognitive decline by an average of seven years. The benefits of exercise seemed to plateau at around 7,500 steps. Those who got more did not see additional benefits in terms of preserving cognitive skills.
Interestingly, physical activity did not seem to affect beta-amyloid levels. Rather, the scientists found that most of the brain benefits of exercise appeared to be driven by slower buildup of a protein called tau, another hallmark of Alzheimer’s disease. As the toxic protein builds up in the brain, it forms spaghetti-like tangles within brain cells, choking them off and speeding the progression of cognitive decline.
Physical activity had far less impact on either cognitive decline or tau buildup in those participants with low levels of beta-amyloid buildup at the study’s start. The findings suggest that moderate exercise may be especially beneficial for those who are at higher risk of Alzheimer’s disease. By slowing the buildup of tau tangles in the brain, exercise appears to slow the progression of cognitive decline. Exercise may act to slow disease onset, long before memory loss and thinking deficits become apparent.
The study, published in the journal Nature Medicine, “sheds light on why some people who appear to be on an Alzheimer’s disease trajectory don’t decline as quickly as others,” said Dr. Jasmeet Chhatwal, the study’s senior author and a researcher in the department of neurology at Mass General Brigham in Boston. “Lifestyle factors appear to impact the earliest stages of Alzheimer’s disease, suggesting that lifestyle changes may slow the emergence of cognitive symptoms if we act early.”
More study is needed to better understand the effects of physical activity on brain health. One idea is that exercise boosts blood flow to the brain, helping to clear toxins that can damage and kill healthy brain cells, but more research is needed to see if that is the case. The study was observational, so cannot prove that exercise directly leads to better brain health. But the findings add to growing evidence that staying active is critical for healthy brain aging. Even taking a few thousand extra steps a day—about 2,000 steps equals a mile, and you can get extra steps in doing chores or gardening or choosing to park farther from the entrance to the supermarket—may have outsized benefits for brain health years down the road.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Wai-Ying Wendy Yau, Dylan R. Kirn, Jennifer S. Rabin, et al: “Physical activity as a modifiable risk factor in preclinical Alzheimer’s disease.” Nature Medicine, November 3, 2025
