Taking a pleasant daily stroll could help slow the protein buildup and cognitive decline associated with Alzheimer's disease, new research reveals.
In a careful study of lifestyle habits, medical data, and brain scans taken of hundreds of senior volunteers, a team led by Mass General Brigham in the US found that even a modest level of physical activity may be sufficient to put the brakes on the disease's progression.
The results suggest that a sedentary lifestyle could play a significant role in Alzheimer's decline – but that also makes it an easy target for intervention.
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Alzheimer's disease is a progressive, degenerative condition characterized by continued degradation in short-term memory. It's also prevalent: An estimated one in three people over the age of 85 lives with Alzheimer's disease.
Scientists are yet to find a cure, but understanding how it works can at least help develop therapeutic strategies.
To investigate the effect of exercise on the progression of Alzheimer's, a team led by neurologist Wai-Ying Wendy Yau studied 296 participants in the Harvard Aging Brain Study (HABS).
These participants, aged between 50 and 90, had no cognitive impairment at the time the study commenced. The study tracked them for up to 14 years, monitoring for, among other things, markers of Alzheimer's disease.
This included scans for amyloid and tau – the two proteins whose buildup is associated with the disease – as well as ongoing cognitive tests. The participants' physical activity was also quantified using wearable pedometers.
The results showed no link between physical activity and amyloid buildup, but there was a clear connection with tau accumulation and cognitive decline. Those who participated in moderate levels of physical activity of between 5,000 and 7,500 steps per day noticeably slowed both the rate of tau buildup and cognitive decline.
However, this is where the effect plateaued; more than 7,500 steps a day produced the same effect.
On the other hand, even modest activity – between 3,000 and 5,000 daily steps – slowed the same markers of Alzheimer's, albeit to a lesser extent.
While it is possible that those classed as moderate exercisers were likely to engage in other activities that could explain their outcomes, this trend suggests that physical activity could be an accessible therapeutic target for Alzheimer's prevention. Wearable activity trackers, the authors note, may offer a simple way to monitor and encourage those benefits.
"Taken together," the researchers write, "our findings support targeting physical inactivity as a strategy in future randomized clinical trials to modify the trajectory of tau and cognition in preclinical AD, and potentially provide an easily understood and more attainable physical activity goal for older sedentary individuals at high risk of cognitive decline."
The paper has been published in Nature Medicine.