You probably already know that sitting alone in front of the television or mindless scrolling on social media isn’t great for your mental or physical health. Now, new research suggests that these mentally passive habits might increase your risk of dementia. It also shows how simple changes to everyday activities can improve your long-term brain health.
The study, published in the American Journal of Preventive Medicine, followed more than 20,000 Swedish adults between the ages of 35 and 64 for nearly two decades. Participants tracked their daily activities, including physical activity and how much time they spent sitting.
Researchers then classified sedentary time into two categories. Mentally active behaviors were defined as activities that required focus and deliberate engagement, such as reading a book, doing crossword puzzles or using a computer for work. Mentally passive activities were defined as those involving little cognitive effort, such as watching a TV series.
Researchers found that people who spent more time in mentally passive activities had a significantly higher risk of developing dementia, while those who engaged more in cognitively active pursuits had a lower risk. This difference remained even after accounting for physical activity, meaning that those who led a more sedentary lifestyle still benefited from greater mental engagement.
These results are in line with our understanding of the brain as an organ that constantly adapts to how it is being used. Activities that require attention and problem-solving strengthen neural connections and reinforce networks used for memory and thinking. Low-effort activity does not provide the same stimulation.
Other factors may also play a role, including that mentally passive activities tend to involve prolonged sitting that reduce blood flow to the brain, compared with more engaging activities that involve movement and shifts in focus.
There are two other findings from the study worth noting: First, researchers noted significant benefits with small changes. Adding an hour of mentally active time was linked to about a 4 percent reduction in dementia risk. Replacing mentally passive activity with an hour of something more engaging resulted in about a 7 percent lower risk.
Even better is combining those changes with physical activity. The greatest risk reduction was seen among mentally active participants who also achieved the recommended 150 minutes of moderate to vigorous physical exercise each week.
Practically, this means people could see real benefits in cognitive health from small switches in their daily activities. For instance, choose to read a book instead of watching one more TV show. Stop scrolling on your phone and try a sudoku puzzle. Don’t just listen to whatever songs are on your playlist; find the lyrics and sing along. You could also add mentally active time by picking up a new hobby or honing a skill, such as drawing, dancing, learning a new language or playing an instrument.
Second — and somewhat surprisingly — the effects of mental engagement appeared more pronounced in older adults. This might be because cognitive demands of work earlier in life offer some protection, whereas retired people simply have more time for passive leisure. It might also be that mentally engaging activities have a more direct impact later in life, when the chances of developing dementia are higher for most people. In either case, the takeaway is encouraging because it implies that adding more cognitively stimulating pursuits has benefits no matter a person’s age.
The study’s major drawback is that it cannot rule out reverse-causation. The authors acknowledge that people with stronger baseline cognitive function might be more inclined to choose mentally and physically engaging activities in the first place. Still, the study supports the association between mental and physical activity and dementia risk, adding to the growing body of evidence that lifestyle factors influence brain health.
Among these factors is social connection. Perhaps the most beneficial activities are those that combine interpersonal interaction with mental stimulation and physical exercise. For instance, go for walks with a friend while engaging in a deep conversation. Join a group tai chi class. Tend a community garden, try ballroom dancing or volunteer to tutor for a local literacy program.
Not only can these activities engage the brain and support physical health, but they can also open the door to new friendships and renew a sense of community and purpose.
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