Regularly sitting for hours can be harmful to your body and brain. A new study suggests that keeping the brain active helps counteract some of the harmful effects of a sedentary lifestyle.
By activity it means activities like knitting or solving a puzzle, rather than mindlessly scrolling through videos and photos on your phone or passively staring at a screen.
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Scientists at the Karolinska Institute in Stockholm surveyed 20,811 Swedish adults—mostly women aged 35 to 64—about their weekly physical activity and the amount of daily time they spent in “mentally active” and “mentally passive” sedentary behaviors. They questioned the participants for the first time in 1997 and followed up 19 years later to assess the risk and occurrence of dementia.
Sedentary behavior — prolonged periods of sitting, lying down or reclining — is linked to “important risk factors for dementia,” such as high blood pressure, heart disease, diabetes and obesity, said Mats Hallgren, a senior researcher at the Karolinska Institutet and one of the study’s authors.
However, brain activity is a crucial element to protect against such damage.
The brain “works like a muscle,” he noted. Not using it actively for prolonged periods of time can, in the long run, negatively affect the areas linked to memory and learning.
In the questionnaire, staying mentally active while remaining sedentary included doing office work, attending meetings while sitting, as well as knitting and sewing. Activities such as using a computer to solve a puzzle were considered intellectually stimulating.
Watching television or listening to music while remaining sedentary was classified as a mentally passive activity.
According to the study – published this Thursday in the American Journal of Preventive Medicine—, participants who spent more time in mentally passive sedentary activities had a “significantly higher risk of developing some type of dementia in the future,” Hallgren said.
Concerns about mental decline
Using a statistical model, the researchers then predicted how changes in mental activity would affect the risk of dementia.
They calculated that adding an hour of active mental activity while remaining sedentary reduced the risk of dementia by 4%; Replacing one hour of passive mental activity with an active one reduced the risk by 7%; and combining physical activity—such as walking—with active mental activity reduced the risk by 11%.
The study has limitations. Since the initial questionnaire was conducted almost three decades ago, smartphones, social media, and continuous screen scrolling did not yet exist. A previous review suggested that older adults derived cognitive benefits from phone use, but less is known about this for children and young adults. Furthermore, as it is based on the participants’ self-report, the research does not allow us to conclude whether mentally passive activities increase the risk of dementia, or if, on the contrary, it is people with a higher risk of dementia who tend to carry out more passive activities.
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Dr. Hussein Yassine, a professor of neurology at the Keck School of Medicine of the University of Southern California, speculates that phone and social media use could pose a similar risk by affecting our ability to concentrate.
“It’s going to affect your ability to process information and potentially form synapses in certain areas of the brain that facilitate concentration,” Yassine said. “Therefore, the next time you have an important task or need to concentrate, you will be less able to do so, as your brain networks will have been hijacked by this passive reception.”
Adam Brickman, a professor of neuropsychology at Columbia University, noted that the rise of short-form content — like that of TikTok — has exponentially increased mentally passive behaviors.
“When you consider how children—and even adults—spend their time passively watching content that I don’t think any of us would classify as stimulating or an active activity, it’s clear that this behavior is much more common today than it was in 1997,” said Brickman, who was not involved in the new study.
Recent research has raised concerns about cognitive decline—popularly known as brain rot (or brain rot)—which includes a reduction in attention span that could result from excessive consumption of short-form videos.
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“That kind of incessant displacement—the scrolling— that takes us from one YouTube video to another without stopping to think; “These types of behaviors, when maintained for prolonged periods and repeated over time, have a high probability of being associated with depression, anxiety and other stress-related disorders, compared to more dynamic activities or the use of travel for work purposes,” he explained.
Although technology has evolved, “the neurological pathways that influence dementia remain essentially the same in people today as they were 30 years ago,” Hallgren said.
His advice for reducing the risk of dementia is simple: “Sit less and move more—and do it more often.”
