A new study suggests that older adults at risk of Alzheimer's disease can slow their cognitive decline by taking just 3000 steps a day. Researchers found that this level of activity reduces the buildup of harmful brain proteins and improves cognitive function over time. The findings highlight the potential benefits of regular, moderate exercise for brain health.
In a study published in Nature Medicine, Wai-Ying Wendy Yau at Harvard University and her colleagues examined the physical activity levels of 296 cognitively healthy individuals aged 50 to 90. Participants wore step-tracking devices for one week to measure their activity objectively. Most underwent brain imaging to assess baseline levels of misfolded tau and beta-amyloid proteins, which are linked to Alzheimer's disease. These levels were monitored every two to three years over a follow-up period ranging from three to 14 years, alongside annual cognitive tests evaluating memory and processing speed.
The researchers used statistical modeling to analyze how step counts influenced brain changes and cognition. Among those with above-average beta-amyloid levels at the start, taking 3000 to 5000 steps per day substantially slowed the accumulation of misfolded tau proteins, though it did not affect beta-amyloid. This was associated with a 40 percent slower rate of cognitive decline over an average nine-year follow-up, compared to those taking fewer than 3000 steps, defined as inactive.
Higher activity brought further gains: 5000 to 7500 steps per day led to a 54 percent slower cognitive decline versus inactivity. However, exceeding 7500 steps showed no additional benefits. "Those tau and cognitive benefits eventually plateau," Yau noted.
"[Exercise is] somehow slowing the spread of this tau protein, which is more strongly associated with people developing symptoms [of Alzheimer’s disease] than amyloid-beta," explained Charles Marshall at Queen Mary University of London. Possible mechanisms include reduced inflammation from protein clumps, improved blood flow, or increased protective hormones in the brain.
The study does not prove causation, as undiagnosed impairments might influence exercise levels, and other factors like lifestyle could play a role. Marshall advised against fixating on exact step counts, emphasizing regular, low-intensity activity. Yau called for randomized trials to confirm these effects and isolate exercise's impact.