Here’s how many daily steps may help delay Alzheimer’s symptoms

People at heightened risk of Alzheimer’s disease may be able to slow their cognitive decline by taking more daily steps, a new study suggests.

Researchers found people with early, presymptomatic Alzheimer’s disease who walked 3,000 to 5,000 steps per day appeared to delay their cognitive decline by three years in comparison with those who walked less. And people who walked 5,000 to 7,000 steps per day appeared to delay their decline by seven years, on average. (Depending on your gait, a mile takes around 2,000 steps.)

“If you’re sedentary, even modest activity could help slow down that process,” said Wai-Ying Wendy Yau, the lead author of the study and a cognitive neurologist at Mass General Brigham.

The study included close to 300 older adults, some of whom had brain scans that indicated they were at higher risk of Alzheimer’s due to the buildup of amyloid beta.

The researchers followed participants for an average of nine years and found that those who took relatively more steps had a slower build up of tau, another type of protein that can tangle and disrupt the communication between brain cells.

The researchers found an association between a person’s step count and the trajectory of their cognitive decline — not a cause-and-effect, Yau said.

Still, the findings suggest regular physical activity may help slow the progression of early, presymptomatic Alzheimer’s disease. Yau said she hopes the findings are empowering for people who are looking for practical ways to protect their brain as they age.

“Exercise is a hard habit to build, but I like to tell my patients every little bit helps,” Yau said. “Every step you take in the right direction helps with brain health.”

The paper, which was published in Nature Medicine, is part of the Harvard Aging Brain Study, which started 15 years ago to better understand how changes that can be detected on brain scans contribute to cognitive decline. And in this study, researchers wanted to understand whether physical activity — measured by steps taken per day — could protect against a decline in cognitive function, Yau said.

Physically active older people are less likely than sedentary people to develop Alzheimer’s disease or other forms of memory loss and cognitive decline. And studies in mice and rats suggest that greater physical activity can slow the progression of the disease. But it’s not clear whether exercise confers the same benefits in humans, Yau said.

The participants, who ranged in age from 50 to 90 and didn’t have dementia or other memory issues when the study began, underwent PET scans so researchers could measure the amount of amyloid beta and tau in the brain. And the volunteers wore a pedometer for seven days at the start of the study to determine their average daily step count.

Then, the researchers analyzed how a participant’s step count related to the levels in amyloid beta and tau in the brain, as well as their cognitive and daily function over time.

Researchers don’t know exactly why exercise may be beneficial for cognitive health, Yau said. One plausible explanation is that greater physical activity may improve blood flow to the brain or reduce inflammation, which could slow the progression of Alzheimer’s disease, Yau said.

One limitation in the study is that the pedometer measured steps taken per day but the researchers don’t know whether those steps were taken walking or running, Yau said. And they didn’t record whether participants did regular resistance training, swimming or other forms of exercise.

“Other studies have shown that different types of physical activity, beyond walking, is beneficial for brain health,” Yau said. “An important next step to look at is to clarify what aspects of physical activity — intensity, duration, pattern — is the most important in preclinical Alzheimer’s disease.”

The study cohort also consisted of highly educated, predominantly non-Hispanic White individuals, which may limit the generalizability of the findings, Yau said.

Ronald Petersen, a professor of neurology at Mayo Clinic in Rochester, Minnesota, said that the study has a “solid methodology” and that the findings are informative but still just an association.

“We must be cautious in generalizing to a broad population,” Petersen said. “We still do not know the mechanisms and influences of exercise.”

Epidemiological studies show a lifelong habit of moderate-to-vigorous physical activity is associated with a lower risk of Alzheimer’s disease, said John Thyfault, the director of KU Diabetes Institute and a professor of cell biology and physiology at the University of Kansas Medical Center.

But exercise programs for older adults who already have early signs of mild cognitive impairment have “mixed results” on slowing the progression of the disease. A person’s lifelong exercise patterns likely have a more robust effect on delaying or preventing Alzheimer’s disease than a six-month trial, he said.

No matter what, walking more — and regular exercise — “will promote hundreds of other positive adaptations in your body” that will mitigate or delay side effects of the disease to some degree, Thyfault said.

“There will be no negative side effects to increasing walking time and physical activity,” Thyfault said. “All of the outcomes will be positive.”