Heavy TV watching associated with smaller brain structures, study finds

“Turn off that TV, it’ll rot your brain!” has been a household refrain for decades. While “rot” might be too strong a term, researchers are finding that the overall sentiment could have some merit.

A study published recently in Alzheimer’s and Dementia: Journal of the Alzheimer’s Association revealed that those who reported watching TV “very often” in midlife later exhibited reduced volume in areas of the brain associated with memory, smaller frontal and occipital lobes, and areas of damage in the brain’s white matter that are associated with aging, stroke risk, cognitive decline and dementia.

“For years we’ve focused on how much people sit. Our findings suggest we should also pay attention to what they’re doing while they’re sitting,” says David Raichlen, professor of biological sciences and anthropology at the USC Dornsife College of Letters, Arts and Sciences and a senior author of the study.

The findings weren’t just due to TV viewing’s sedentary nature. The study found that other types of sedentary activities did not have the same associations, indicating that what one does while sitting may matter much more than previously thought.

Watching changes

The researchers analyzed data from about 1,700 adults, average age 53, who enrolled in the Atherosclerosis Risk in Communities (ARIC) Study between 1987 and 1989. ARIC is a long-running study of the U.S. population designed to investigate cardiovascular and brain health.

Participants were asked how frequently, on a scale ranging from “never/seldom” to “very often,” they watched television during their leisure time and how much of their workday they spent sitting.

More than two decades later, participants underwent brain MRI. Compared with people who reported “never” or “seldom” watching TV, those who watched TV “very often” showed widespread structural differences across the brain.

The researchers found smaller volumes in areas associated with early signs of Alzheimer’s disease and more white matter hyperintensity volumes, an indicator of cerebral small blood vessel disease associated with cognitive decline and dementia. These participants also had smaller occipital and frontal lobes, regions associated with visual processing and executive functioning.

Differences persisted even when the researchers controlled for factors such as physical activity, diabetes, body mass index, smoking, and alcohol use.

Of note, the researchers relied on self-reported data for TV consumption, which can be less precise than timed tracking. Study participants also did not undergo a baseline MRI. Future research could begin with a baseline MRI to more concretely demonstrate changes over time.

Not all sitting is made the same

Strikingly, the sedentary element of TV watching didn’t appear to be the main driver for these changes.

Those who reported high amounts of sitting at work actually had larger frontal and occipital lobes, as well as reduced white matter hyperintensity volumes, indicating better brain health than among those who sit to watch TV. This could be due to the intellectually stimulating nature of many sit-down jobs, say the study authors.

Men appeared to be particularly vulnerable to these changes. When the MRI scans were separated by sex, researchers found that most of the changes to the brain, both from TV watching and occupational sitting, were seen in men.

Such findings indicate there is still more research to be done on this complex topic. However, we might eventually see a different approach to health guidance around sedentary activities. Rather than just directing their patients to move more, for example, physicians might recommend they reduce television time and add cognitively engaging activities for when they do sit.

“We frequently encourage the public not to spend too much time sitting down, but experts may want to expand that recommendation to encompass the activities done while sitting, since those seems to have distinct impacts on brain health,” says study corresponding author Natan Feter, postdoctoral scholar in the Human and Evolutionary Biology program at USC Dornsife.

Reference:

Feter N, Nanda A, Hourihan S, et al. Associations of distinct sedentary behaviors with cortical, subcortical, and white matter hyperintensity volumes: Evidence from the ARIC study. Alzheimer's Dement. 2026; 22:e71582. https://doi.org/10.1002/alz.71582