The number of daily steps you take may delay Alzheimer’s progression

Walking at least 60 minutes a day provides real benefits to both the heart and brain, experts say. (Oscar Wong/Moment RF/Getty Images via CNN Newsource)

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 proteins are 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.”

By Sandee LaMotte, CNN