Even light exercise such as walking improves brain health
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Older people who are especially at risk Alzheimer's disease could slow cognitive decline by taking just 3,000 steps a day. Why counting steps might have this effect is unclear, but it may be due to the effect of regular exercise on inflammation or blood flow to the brain.
Previous studies that link regular exercise To reduce cognitive decline, there has been a heavy reliance on people recalling their activity level and rarely exploration of why staying active might have this effect.
To remove such restrictions, Wai-Ying Wendy Yau of Harvard University and her colleagues analyzed the physical activity of 296 cognitively healthy people aged 50 to 90 who wore a step-tracking device for one week to objectively measure their activity levels.
Most participants had their brains scanned to reveal baseline levels of misfolded proteins called tau and beta-amyloid, the accumulations of which are believed to cause Alzheimer's disease. These levels were then typically measured every two to three years over a follow-up period of three to 14 years. Participants also took yearly cognitive tests that assessed things like their memory and processing speed.
By feeding data on step counts, brain imaging, and cognitive tests into a statistical model, the researchers assessed how exercise affected cognitive decline. They found that among participants with above-average levels of misfolded beta-amyloid in the brain at the start of exercise, 3,000 to 5,000 steps per day appeared to significantly slow the accumulation of misfolded tau, but not beta-amyloid.
“[Exercise is] somehow slowing down the spread of this tau protein, which is more closely linked to people developing symptoms. [of Alzheimer’s disease] than beta-amyloid,” says Charles Marshall at Queen Mary University of London.
It was also associated with a slowing of their rate of cognitive decline by about 40 percent over an average follow-up period of nine years, compared with those who took fewer than 3,000 steps per day, defined as inactivity. The researchers did not have data to assess whether any of the participants were diagnosed with Alzheimer's disease during the follow-up period.
Meanwhile, walking 5,000 to 7,500 steps a day appeared to further slow the accumulation of tau, leading to cognitive decline 54 percent slower compared to inactivity. But walking more than 7,500 steps a day did not lead to further cognitive benefits. “These tau and cognitive benefits eventually trickle down,” Yau says.
Researchers haven't figured out how regular exercise might have this effect, but it may be due to physical activity that reduces inflammationwhich is believed to result from the misfolding of beta-amyloid and tau, which then disrupts nerve connections and kills cells. Exercise can also increase blood flow or levels protective hormone into the brain.
However, this study does not prove that walking 5,000 steps a day slows or delays cognitive decline. Existing disorders that haven't yet been diagnosed or even noticed can affect people's ability or motivation to exercise, Marshall says. Other lifestyle or socioeconomic factors, some of which the team tried to account for, may also influence tau activity and levels, he said.
However, regular exercise has many benefits. health benefits, is free to do and has very few (if any) side effects, which may encourage people to take at least 3,000 steps a day, although the exact effects on cognitive function are unclear. “My advice to people is don’t get too hung up on the magic number for [step count] goal,” Marshall says. – I think, [what’s] “What's more important is the idea of doing something regularly, and it doesn't have to be a lot and it doesn't have to be high intensity, it's more about doing some physical activity with high regularity.”
Previous studies show that sustainable lifestyle changes – including exercise – improve cognitive decline. But further studies in which people are randomly assigned to achieve different numbers of daily steps are needed to separate the effects of exercise from other lifestyle changes and establish whether they actually slow tau accumulation, Yau says.
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