If you’ve reached midlife and love a good Netflix binge ― we’re talking enough to trigger the “Are you still watching?” prompt ― we’ve got some unfortunate news for you: According to a new study from researchers at the University of Southern California, watching TV often in midlife is linked to some worrisome brain changes later in life.
The study, published in Alzheimer’s & Dementia: Journal of the Alzheimer’s Association, found that adults who reported watching television “very often” during midlife later had smaller memory-related brain regions. These adults also showed reduced volume in the frontal and occipital lobes and more damage to the brain’s white matter ― changes associated with aging, increased stroke risk, cognitive decline and dementia.
Previous research on sedentary behavior and its impact on brain health has largely focused on how long people sit, said Natan Feter, a postdoctoral research associate in the department of biological sciences at USC and one of the study’s authors. For instance, a 2023 Harvard study found that spending 10 or more hours a day physically inactive was linked to a higher risk of developing dementia later in life.
But Feter and his team wanted to dig deeper. Instead of looking only at the number of hours people spent sitting, they wanted to know whether what people were doing while they sat made a difference for brain health.
“What we found is that what you do while sitting ― not just how long you sit ― seems to predict your brain volume 20 years in the future,” Feter told HuffPost. “Spending more time watching television was associated with smaller brain volumes in regions especially vulnerable to Alzheimer’s disease and with greater signs of damage to the brain‘s small blood vessels.”
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To conduct the study, researchers analyzed data from about 1,700 adults in the long-running U.S. Atherosclerosis Risk in Communities (ARIC) Study, who were about 53 years old on average when they enrolled between 1987 and 1989. Participants reported how often they watched TV during their free time and how much of their workday they spent sitting.
More than 20 years later, participants underwent brain MRI scans. Compared with those who said they “never” or “seldom” watched TV, people who reported watching it “very often” showed widespread structural differences throughout the brain.
The group that watched TV most often also had smaller frontal and occipital lobes. The frontal lobes are involved in skills like planning, decision-making and other executive functions, while the occipital lobes help the brain process visual information. These differences held up even after researchers accounted for other factors that can affect brain health, including physical activity, diabetes, body mass index, smoking and alcohol use.
“Other common sedentary activities showed the opposite pattern, suggesting that what we do while sitting may matter even more than how long we sit,” he explained.
What is it about TV consumption that’s so detrimental to our brain health compared to say, knitting or playing Wordle?
Feter said their study can’t determine the exact reasons, but there are several plausible explanations. For one, television viewing is typically a highly passive activity that requires relatively little cognitive engagement.
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“It’s also more likely to occur in prolonged, uninterrupted sitting bouts and is often accompanied by unhealthy behaviors, such as snacking or reduced social interaction,” he said. “In contrast, activities like reading, computer use, or hobbies often involve greater mental stimulation.”
One important limitation is that this was an observational study, so the researchers can’t can’t conclude that television viewing directly causes these brain changes. Sitting time was also self-reported, too, Feter said, which could introduce some measurement error. (We get it; not everyone wants to cop to how many hours of their lives they’ve lost to “Love Is Blind” episodes.)
“I think future studies ― using wearable devices, repeated brain imaging and intervention designs ― will help clarify whether reducing television viewing or replacing it with more cognitively engaging activities can help preserve brain health over time,” Feter said.