THURSDAY, March 26, 2026 (HealthDay News) -- Mentally passive sedentary behavior may increase the risk for dementia, while mentally active sedentary behavior may reduce the risk, according to a study published online March 26 in the American Journal of Preventive Medicine.
André O. Werneck, Ph.D., from the Universidade de São Paulo in Brazil, and colleagues examined associations of mentally passive and mentally active sedentary behaviors with incident dementia using data from the Swedish National March Cohort, including 20,811 adults aged 35 to 64 years.
The researchers identified 569 incident cases of dementia during a median follow-up of 19.2 years. In crude models, mentally passive sedentary behavior was associated with a higher incidence of dementia (hazard ratio, 1.16), but this finding was not seen in adjusted models. The risk for developing dementia was lower in association with each additional one hour per day of mentally active sedentary behavior (hazard ratio, 0.96). A significant age interaction was seen, with a higher protective effect of mentally active sedentary behavior among older participants (aged 50 to 64 years). An increase of one hour per day of mentally active sedentary behavior, while maintaining passive sedentary behavior and light and moderate-to-vigorous physical activity constant, was associated with a reduced risk for incident dementia (hazard ratio, 0.89). Likewise, substitution of one hour per day of passive with mentally active sedentary behavior was associated with a reduction in the risk for incident dementia (hazard ratio, 0.93).
"How we use our brains while we are sitting appears to be a crucial determinant of future cognitive functioning and, as we have shown, may predict dementia onset," lead author Mats Hallgren, Ph.D., from Deakin University in Geelong, Australia, said in a statement.