American Journal of Preventive Medicine, March 2026 (online) | André O. Werneck et al. | Swedish National March Cohort
Research published in the American Journal of Preventive Medicine in March suggests that not all sedentary time carries the same risk for the brain. A team led by André O. Werneck tracked 20,811 Swedish adults over 19 years, sorting their sedentary hours into mentally passive (TV, scrolling, listening to music) and mentally active (reading, office work, engaged hobbies).
Swapping one hour of passive screen time for a mentally engaging activity each day was linked to a 7% lower risk of dementia. The protective effect was strongest among participants aged 50 to 64. Physical activity appeared beneficial overall but did not offset the cognitive cost of passive hours.
“The concern raised by this study is not so much about screens themselves, but more about prolonged periods of low-engagement behavior…such as mindless scrolling or continuously consuming content on social media,” said Leana Wen, a professor of health policy at George Washington University.
Small substitutions add up: a puzzle instead of a rerun, a phone call instead of a feed, a book instead of a scroll—all of these act in the aging brain’s favor.
