Bolstering the notion that a strong body equals a strong mind, new research indicates that the more inactive seniors are, the higher their risk for dementia.
The finding stems from a look at the onset of dementia among nearly 50,000 Brits.
All were at least 60 years old when information about typical daily activity routines was entered into the UK Biobank database at some point between 2006 and 2010.
Their risk for dementia was then tracked for an average of about seven years.
"We looked into whether sitting too much can increase the risk of getting dementia," said lead author David Raichlen, a professor of biological sciences and anthropology at the University of Southern California. "Turns out, if you're sedentary for over 10 hours a day, there's a higher risk."
Compared to spending nine hours a day on the proverbial couch, 10 hours of inactivity were associated with an 8% higher risk for dementia among seniors.
And more inactivity was even riskier: Seniors who clocked 12 hours a day of inactivity -- be it at one stretch, or over 24 hours -- saw their risk for dementia spike by 63%. Those who sat around for 15 hours a day had a stunning 320% increase in dementia risk.
The study doesn't prove inactivity causes dementia, Raichlen stressed.
It could be that other issues that might lead to inactivity -- such as poor physical health or even the undiagnosed early stages of dementia itself -- could be the true culprit when it comes to the increased dementia risk.
But if inactivity is linked to higher dementia risk, why might that be?
"It is possible that reduced blood flow to the brain can help explain these results," Raichlen said. Or it could owe to the fact that inactivity is also associated with a higher risk for cardio-metabolic illnesses, including heart attacks, strokes, diabetes and/or liver disease.
"[There is] definitely more work to do to better understand the mechanisms underlying these associations," he said.
Participants in the study were residents of England, Scotland and Wales (average age: 68). None had signs of dementia when basic health information was gathered at enrollment.
Between 2013 and 2015, they wore an activity tracker on their wrist around the clock for three to seven days.
By 2021, just over 400 men and women had been diagnosed with dementia.
The team pointed to prior research indicating that, on average, Americans are sedentary for about 9.5 hours a day. This study found no evidence that this typical American inactivity is linked to any uptick in dementia risk.
But once sedentary behavior averaged 10 hours or more, seniors did appear to have an increased risk of dementia.
After years of inactivity, might getting moving turn that around?
"It's hard to say based on our dataset," Raichlen said. "In my opinion, it is never too late to sit less and move more. But we do not have the data yet to say whether there are key times in life where sitting is more strongly linked to dementia risk."
Claire Sexton is senior director of scientific programs and outreach at the Alzheimer's Association in Chicago. She expressed little surprise after reviewing the findings.
"There have been a number of studies that have previously reported an association between sedentary time and risk of dementia," Sexton said. "However, reports that did not find an association have also been published. Therefore, additional research on possible associations is welcome."
She cautioned that while the pool of participants enrolled in the study was large, it may not be representative of all American seniors. And, she added, while regular physical activity is key to overall health, it "cannot be viewed in isolation."
The role that activity may play in terms of dementia risk "must be considered in combination with one's total behavior and lifestyle," Sexton said. That includes "healthy diet, education, head injury, sleep, mental health and the health of your heart/cardiovascular system and other key bodily systems."
The findings were published Tuesday in the Journal of the American Medical Association.
There's more about physical activity and brain health at the Alzheimer's Association.
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