Keeping the brain busy while sitting, through puzzles or knitting, may cut dementia risk, a study suggests.
Researchers surveyed more than 20,800 Swedish adults, mostly women aged 35 to 64, about their weekly physical activity and how much time each day they spent in what they classed as ‘mentally active’ and ‘mentally passive’ sedentary behaviour.
Participants were first questioned in 1997 and followed up 19 years later to assess their dementia risk and status.
Those who spent more time in mentally passive sitting had a significantly higher risk of developing some type of dementia in the future, the findings suggested.
The study was carried out by scientists at the Karolinska Institute in Stockholm.
Mentally active sedentary behaviour included office work, sitting in a meeting, knitting, sewing and using a computer to solve a puzzle.
Watching television or listening to music while sitting still counted as mentally passive.
Using a statistical model, the researchers calculated that adding an hour of mentally active behaviour while sedentary cut dementia risk by 4 per cent.
Replacing an hour of mentally passive behaviour with mentally active behaviour cut the risk by 7 per cent. Combining physical activity, such as walking, with active mental behaviour cut the risk by 11 per cent.
Mats Hallgren, a principal researcher at the Karolinska Institute and an author of the study, said sedentary behaviour, meaning long periods of sitting, lying down or reclining, is linked to “major risk factors for dementia,” such as high blood pressure, heart disease, diabetes and obesity.
However, he said the brain “works like a muscle,” and not actively using it for extended periods can eventually negatively affect the areas linked to memory and learning.
The study has limitations.
Because the initial questionnaire was carried out almost three decades ago, smartphones, social media and endless scrolling did not exist.
An earlier review suggested that older adults gained cognitive benefits from phone use, but less is known about children and young adults
The research was also based on self-reporting, meaning it cannot show whether mentally passive activities increase the risk of dementia, or whether people already at greater dementia risk are simply more likely to engage in passive activities.
Dr Hussein Yassine, a professor of neurology at the University of Southern California Keck School of Medicine, suggested that phone and social media use may pose a similar risk by affecting the ability to concentrate.
“It’s going to be affecting your ability to process information and potentially build synapses in certain areas in the brain that help with concentrating,” Yassine said.
“So the next time you have a serious task or you need to concentrate, you’re less capable because your brain networks have been hijacked by this passive reception.”
Synapses are the connections between nerve cells in the brain that allow them to communicate with one another, and building new ones is considered important for learning and memory.
Adam Brickman, a professor of neuropsychology at Columbia University, who was not associated with the study, said the rise of short-form content like TikTok has exponentially increased mentally passive behaviour.
“If you think about how kids, even adults, are spending their time passively looking at content that I think none of us would classify as stimulating or active behaviour, it’s certainly a lot higher today than it was in 1997,” Brickman said.
Recent research has raised concerns about cognitive deterioration, sometimes called ‘brain rot’, including shorter attention spans that may come with heavy consumption of short-form video.
“This sort of nonstop-without-thinking scrolling from one YouTube video to the next, those sorts of behaviours when you’re sitting for a very long time, if they’re repeated over time, are likely to be associated with depression and anxiety and stress-related conditions, compared to more active engagements and doing work-type scrolling,” he said.
Hallgren said that even though technology has changed, “the pathways that affect dementia fundamentally are the same in people today that they were 30 years ago.”
His advice for lowering dementia risk was simple: “Sit less and move more, more often.”
