Engaging in “mentally active” activities versus “mentally passive” ones while sitting or lounging may affect your risk for dementia, according to a recent study.

In a study published in the American Journal of Preventive Medicine last month, researchers evaluated over 20,000 adult participants in Sweden, most of whom were women. Researchers administered a baseline questionnaire to participants in 1997 to assess their mentally passive sedentary behaviours, such as watching TV and listening to music. They also assessed their mentally active sedentary behaviours, such as office work or knitting and sewing. Their light and moderate-to-vigorous physical activity was also assessed using questionnaires. The participants were evaluated for incident dementia nearly two decades later.

The study found that mentally passive sedentary behaviour ― for example, watching TV ― was associated with a higher incidence of dementia. But adding mentally active sedentary behaviour (needlepointing, anyone?) showed promising outcomes.

Researchers found that each additional hour of mentally active sedentary behaviour a day was associated with a 4% lower risk of dementia — and that adding mentally active sedentary behaviour showed a higher protective effect for participants aged 50 to 64.

The study also found that replacing one hour of mentally passive sedentary behaviour with one hour of active sedentary behaviour was associated with a 7% decreased risk. What’s more, adding one hour of mentally active sedentary behaviour, while maintaining the same passive sedentary behaviour and light and moderate-to-vigorous physical activity, was associated with a 11% decrease in incident dementia risk.

Researchers noted that the study had some limitations. For starters, the study began in 1997, before the vast introduction of smartphones, social media and video streaming — which are now very common ways people engage in sedentary behaviour.

Dr. Hussein Yassine, a professor of neurology at the University of Southern California Keck School of Medicine, emphasised to NBC News that phone and social media usage, which are considered mentally passive behaviours, may pose risks to our 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 told the outlet. “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.”

Among several other limitations cited in the study: Researchers pointed out that cognitive assessments were not done at the start, and it’s possible the sample may have included more prevalent cases of dementia, which may have resulted in a bias in the results.

Dr. Leana Wen, an emergency physician and clinical associate professor at George Washington University and CNN wellness expert, told CNN that one explanation for the results of the study could be due to the fact that “the brain benefits from being challenged.”

“Cognitive engagement helps maintain neural connections and may support what’s called cognitive reserve, which is the brain’s ability to adapt and compensate for changes over time,” she said. “When people spend long periods in activities that require very little mental effort, those pathways may not be stimulated in the same way. Over the course of months and years, that lack of engagement could contribute to decline in memory and thinking.”

Wen cautioned, though, that the study doesn’t prove cause and effect.

“It’s possible that people with better baseline cognitive function are more likely to choose mentally engaging activities,” she said. “So, while the findings are compelling, they should be interpreted as an association rather than proof that choosing passive activities directly leads to dementia.”

Research has shown that engaging in mentally stimulating activities, in addition to staying physically active, can be beneficial for your brain health.

Dr. Dylan Wint, director of the Cleveland Clinic Lou Ruvo Center for Brain Health, previously emphasised the importance of strengthening the brain in an interview with HuffPost.

“You could try brain games, a new hobby, taking a class at a college or community centre, or learning a new language or instrument,” Wint said. “When determining whether an activity can have some cognitive benefit, what’s most important is that you are challenged and learning.”