Heavy television viewing in middle age was linked to a troubling brain signature more than 20 years later.

Television may be doing more than filling quiet hours. A long-term study suggests that people who watched it most frequently in middle age later showed structural brain differences linked to memory loss, vascular damage, and dementia.

The findings, published in Alzheimer’s and Dementia: Journal of the Alzheimer’s Association, challenge the idea that all sitting affects the brain in the same way. Time spent watching television was associated with poorer brain health decades later, while sitting at work showed a very different pattern.