Mentally active sitting may reduce dementia risk

A 19-year Swedish study of 20,811 adults found that more mentally passive sitting (for example, watching TV) was linked with a higher future dementia risk, and researchers estimated that replacing passive sitting with mentally active sedentary activities or adding physical activity was associated with lower modeled risk.

A long-term Swedish study examined links between types of sedentary behavior and later dementia risk. Researchers at the Karolinska Institute surveyed 20,811 adults in 1997 about their weekly physical activity and time spent in mentally active versus mentally passive sedentary behaviors, then followed participants for 19 years and reported findings in the American Journal of Preventive Medicine. Mentally active sedentary tasks were defined to include activities such as office work, meetings, knitting, sewing and puzzle solving, while mentally passive sitting included watching TV or listening to music. The study used statistical models to estimate how shifts in mental activity and physical activity might relate to dementia risk. Key findings: - The cohort included 20,811 Swedish adults, mostly women aged 35–64 at the initial survey, with dementia outcomes assessed about 19 years later. - Mentally active sedentary behaviors were categorized as office work, meetings, knitting or puzzles; mentally passive behaviors included watching TV or listening to music. - Participants reporting more mentally passive sitting had a significantly higher risk of developing some type of dementia in the future, as reported by the researchers. - Modeling suggested that adding one hour of mentally active sedentary behavior was associated with a 4% lower dementia risk, replacing an hour of passive sitting with active sitting was associated with a 7% lower risk, and combining physical activity with mentally active behavior was associated with an 11% lower risk. - The authors note limitations: the baseline questionnaire was collected before widespread smartphone and social media use, the data are self-reported, and the study cannot establish causation. Summary: The study reports an association between more mentally active sitting and lower modeled dementia risk and highlights questions about how changes in technology and behavior since 1997 affect those relationships. Undetermined at this time.