You may want to think twice before binge-watching that new Netflix series, especially if you’re over 50.
A new study, published July 10 in Alzheimer’s & DementiaTrusted Source, found that people who reported watching TV “very often” during midlife had reduced volume in several brain regions more than 20 years later.
The findings weren’t solely explained by sedentary behavior, either.
People who spent much of the workday sitting for their jobs didn’t show the same brain changes, suggesting that what you do while sitting may matter as much as—or more than—how long you spend sitting.
“This study matters because [it] is a more practical and realistic message than simply telling people to ‘sit and watch TV less.’” Dung Trinh, MD, internist of MemorialCare Medical Group and Chief Medical Officer of Healthy Brain Clinic in Irvine, CA, who wasn’t involved in the study, told Healthline.
How watching a lot of TV may change your brain
The study used data from 1,700 adults with an average age of 53 who had enrolled in the Atherosclerosis Risk in Communities (ARIC) Study between 1987 and 1989. This is a long-running study in the United States designed to investigate cardiovascular and brain health.
Participants were asked how frequently they watched TV during leisure time, on a scale from “never/seldom” to “very often.” They were also asked how much of their workday they spent sitting.
Over 20 years later, each participant was given a brain MRI. When the researchers compared those who “never/seldom” watched TV to those who “very often” watched, they found that those who watched TV more often showed widespread structural differences across the brain.
The researchers found smaller volumes in brain areas that are associated with memory and early signs of Alzheimer’s disease. They also found greater white matter hyperintensity volumes, which are an indicator of cerebral small blood vessel disease associated with cognitive decline and dementia.
These participants were also found to have smaller frontal and occipital lobes, which are associated with visual processing and executive functioning.
The differences persisted even when the researchers controlled for factors, such as:
- body mass index (BMI)
- physical activity
- hypertension (high blood pressure)
- diabetes
“Smaller brain volumes do not necessarily mean that someone will develop dementia, but they are considered markers of brain aging and have been linked to a higher risk of future cognitive decline,” said Natan Feter, PhD, Postdoctoral Research Associate, Department of Biological Sciences, University of Southern California, and study author.
“It’s important to emphasize that our study shows an association, not a cause-and-effect relationship. The findings suggest that reducing prolonged TV viewing and replacing some of that time with more engaging activities, whether physical, social, or mentally stimulating, may be beneficial for maintaining brain health as we age,” he told Healthline.
Brain changes not linked to sedentary behavior alone
The findings suggest that sedentary behavior alone wasn’t responsible for the observed brain differences.
The researchers noted that people who reported high amounts of sitting while working actually had larger frontal, parietal, and occipital lobes. They also had reduced white matter hyperintensity volumes. This indicates better brain health than those who sat watching TV.
“Our study found that what you do while sitting can predict your brain structure in the next 24 years,” said Feter. “TV viewing is often prolonged, cognitively passive, and may also be accompanied by other unhealthy behaviors, such as snacking or reduced social interaction, which together could contribute to poorer brain health over time.”
Men may be particularly vulnerable to the brain changes associated with frequent TV watching. When the researchers analyzed the results by sex, they found that the associations between heavy TV viewing and lower brain volumes were observed primarily in males.
These findings may indicate that, in the future, there may be a different approach to health guidance on sedentary behaviors.
“The larger idea and recommendation is replacing passive sedentary time with mentally active sedentary time, so the practical takeaway is to look for easy substitutions in daily life,” said Trinh.
He suggested replacing part of their TV time with reading, writing, puzzles, planning, crafts, or learning something new.
“The goal is not to eliminate passive rest, but to build more cognitively engaging moments into the day,” Trinh told Healthline.
Feter also noted that incorporating movement throughout the day remains important.
“But spending leisure time in cognitively or socially engaging activities may also help support healthy brain aging. More research is needed, but our findings reinforce that the quality of our daily behaviors may matter just as much as the quantity.”
