In older adults at higher risk of Alzheimer’s disease, even “modest” increases in daily steps seemed to help slow cognitive decline, researchers say.
“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 volunteerswore 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 show early signs of mild cognitive impairment have “mixed results” on slowing the progression of the disease. A person’s lifelong exercise patterns probably 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.”
The number of daily steps you take may delay Alzheimer’s progression
Increasing the number of steps you take every day may slow cognitive decline in older adults who already have biological signs of early Alzheimer’s disease, according to a new observational study.
The presence of beta amyloid and tau proteinsare hallmark signs of Alzheimer’s. Amyloid can begin to accumulate in the spaces between neurons as early as one’s 30s, potentially affecting communication between brain cells. As amyloid deposits grow, they can lead to a rapid spread of abnormal tau proteins, which form tangles inside brain cells, thus killing them.
“Physical activity may help slow the buildup of tau — the protein most closely linked to memory loss — and delay cognitive decline in people with early Alzheimer’s,” said lead study author Dr. Wai-Ying Wendy Yau, a neurologist and memory disorders physician scientist at Massachusetts General Hospital in Boston.
Cognitive decline was delayed by an average of three years for people who walked 3,000 to 5,000 steps per day, and by seven years in individuals who walked 5,000 to 7,500 steps per day, Yau said in an email.
While the research is informative, relying on a specific number of steps per day to prevent Alzheimer’s is too simplistic, said neurologist Dr. Richard Isaacson, director of research at the Institute for Neurodegenerative Diseases in Florida. He was not involved in the study.
“I get really cautious about catchy numbers like walking 5,000 or 7,000 steps,” said Isaacson, who conducts studies on cognitive improvement in people who are genetically at risk for Alzheimer’s disease.
“If someone has excess body fat, if someone has prediabetes, if someone has high blood pressure, just walking a certain number of steps won’t be enough,” he said. “Everyone needs their own individualized plan.”
No decline in beta amyloid
The study was small — only 296 people between the ages of 50 and 90 — but researchers used objective measures, which improved the reliability of the 14-year study published Monday in the journal Nature Medicine.
“The strength of this research is the combination of serial highly specialized scans that measure amyloid and tau deposition in the brain, with cognitive assessments and baseline step count. This is unique,” said Masud Husain, a professor of neurology and cognitive neuroscience at the University of Oxford’s medical science division, in a statement. He was not involved in the study.
Steps were measured by pedometer; participants underwent yearly cognitive testing for an average of nine years; and everyone received a PET (or positron-emission tomography) scan at the beginning of the study to measure levels of amyloid and tau. A smaller group received a follow-up PET scan at the end of the study.
While tau buildup slowed by between three and seven years for people who walked up to 7,500 steps per day, people who were sedentary had a significantly faster buildup of tau proteins and more rapid declines in cognition and daily functioning, the study found.
An unusual finding was the lack of a relationship between physical activity and a decline in beta amyloid, which appears before tau.
“Instead, for a given amount of elevated amyloid burden, higher step counts were associated with slower accumulation of tau, which largely explained the relationship with slower cognitive decline,” said Yau, who is also an instructor at Harvard Medical School.
Because the study was only observational, it cannot show a direct cause and effect, Yau said. However, such studies reinforce existing knowledge that what is good for the heart — such as walking, stress reduction, quality sleep and a plant-based diet — is good for the brain, experts say.
“We’ve known for years that mice which exercise on their little wheels have about 50% less amyloid in their brains,” Isaacson said. “While we need more research in people, I’m convinced exercise on a regular basis reduces amyloid buildup and improves cognition.”
