Even modest amounts of daily exercise may slow the progression of Alzheimer’s disease in older people who are at risk of developing the condition, researchers have said.
People are often encouraged to clock up 10,000 steps a day as part of a healthy routine, but scientists found 3,000 steps or more appeared to delay the brain changes and cognitive decline that Alzheimer’s patients experience.
Results from the 14-year-long study showed cognitive decline was delayed by an average of three years in people who walked 3,000 to 5,000 steps a day, and by seven years in those who managed 5,000 to 7,000 steps daily.
“We’re encouraging older people who are at risk of Alzheimer’s to consider making small changes to their activity levels, to build sustained habits that protect or benefit their brain and cognitive health,” said Dr Wai-Ying Yau, the first author on the study at Mass General Brigham hospital in Boston.
Dementia affects an estimated 50 million people worldwide, with Alzheimer’s disease the most common cause. In the UK, more than 500,000 people have Alzheimer’s. The condition is linked to the buildup of two toxic forms of proteins in the brain, namely amyloid-beta plaques and tau tangles.
Yau and her colleagues analysed data from 296 people aged 50 to 90 who were cognitively unimpaired at the beginning of the study. The data included annual cognitive assessments, step counts measured by pedometers, and PET imaging to detect levels of amyloid and tau in the volunteers’ brains.
People with little brain amyloid at the start showed very little cognitive decline or buildup of tau protein over the course of the study. The risk of Alzheimer’s was greater for those with elevated amyloid at baseline, and among them, higher step counts were linked to slower rates of cognitive decline and a delayed buildup of tau proteins. In sedentary individuals, the buildup of tau and cognitive decline was substantially faster, the researchers report in the journal Nature Medicine.
While the scientists cannot rule out reverse causation, where early brain changes in Alzheimer’s causes people to walk less in older age, the data suggests physical activity is protective. “We need randomised clinical trials to prove cause and effect, but it’s very encouraging that physical activity may help to modify someone’s trajectory,” Yau said. “If they have amyloid, they could have a slower rate of decline if they’re more physically active.”
How exercise could help is unclear, but physical activity improves blood flow, reduces inflammation and raises the levels of certain hormones and growth factors, all of which may play a role. “In terms of potential mechanisms, that is the million-dollar question we want to look at in future studies,” Yau said.
Dr Julia Dudley, of Alzheimer’s Research UK, said: “The findings suggest that even a modest amount of walking each day, around 5,000 steps, is linked to a slower buildup of tau protein in the brain, one of the key drivers of Alzheimer’s disease. This gives us a clearer picture of how everyday activity may support brain health and impact the underlying causes of Alzheimer’s.
“More research, including clinical trials, is needed to see the direct impact of physical activity on preventing and slowing the progression of dementia and on underlying disease causes. But studies like this reinforce that simple changes to our lifestyle could help keep our brains healthier for longer.”
