“Turn off the TV, your brain will rot!” has been repeated in families for generations. Although the word “corrupt” is clearly an exaggeration, new research suggests that binge-watching TV may still have a significant impact on brain health.
Recent research published in Alzheimer’s Disease and Dementia: Journal of the Alzheimer’s Association Researchers found that adults who said they watched TV “very frequently” in midlife later had smaller volumes in brain regions associated with memory. They also had decreased volume in the frontal and occipital lobes and increased damage to the brain’s white matter, changes associated with aging, stroke risk, cognitive decline, and dementia.
“For years, we’ve focused on how much people sit, and our findings suggest we should also pay attention to what people do while they’re sitting,” says David Reichlen, professor of biological sciences and anthropology in the USC Dornsif College of Letters, Arts and Sciences and senior author of the study.
Importantly, this result does not seem to be explained by physical inactivity alone. Other sedentary behaviors were not associated with the same brain patterns. This suggests that the types of activities people engage in while sitting may be more important than researchers once thought.
Track your TV habits in midlife
The research team looked at information from about 1,700 adults, with an average age of 53. Participants participated in the Atherosclerosis Risk in Communities (ARIC) study from 1987 to 1989. ARIC is a long-term population study in the United States focused on cardiovascular and brain health.
Participants reported how often they watched television in their free time using a scale ranging from “never/almost never” to “very often.” We also asked how much of their working day they spent sitting.
More than 20 years later, the participants underwent MRI scans of their brains. Compared to people who said they watched TV “never” or “rarely,” those who said they watched TV “very often” showed widespread structural differences across their brains.
Brain areas become smaller and white matter damage increases
People who watched TV frequently watched less in areas associated with early signs of Alzheimer’s disease. They also had more white matter hyperintensity, a sign of cerebral small vessel disease and associated with cognitive decline and dementia.
The same group also had smaller frontal and occipital lobes. The frontal lobes play an important role in planning, decision-making, and other executive functions, while the occipital lobes are central to visual processing.
These differences remained even after the researchers took into account physical activity, diabetes, BMI, smoking, and alcohol intake.
This study had important limitations. Television habits were self-reported, which is generally less accurate than directly measuring viewing time. Participants also did not have an MRI scan at the beginning of the study. Future studies that include baseline imaging may provide stronger evidence of how brain structure changes over time.
Why all sitting positions are not equal
One of the most surprising findings was that sitting itself did not appear to be the main factor behind the observed brain differences.
In fact, participants who spent the majority of their working hours sitting had larger frontal and occipital lobes and reduced white matter hyperintensity. These patterns suggest better brain health than that observed among people who sit and watch TV.
The study authors say one possible explanation is that many sedentary jobs require problem-solving, concentration, and other forms of intellectual stimulation. In other words, mentally active sitting may affect the brain differently than passive TV viewing.
Brain changes were more pronounced in men
Researchers also found differences between men and women. When researchers looked at the MRI data for men and women, they found that men showed most of the brain changes associated with watching TV and sitting at work.
The results suggest that men may be particularly vulnerable to the brain effects associated with these behaviors, but further research is needed to understand why.
The findings highlight the complexity of sedentary behavior and suggest that future health recommendations may need to be more specific. In addition to telling patients to spend less time sitting, doctors may end up encouraging patients to limit screen time and choose more mentally engaging activities while sitting.
“While we frequently advise the public not to spend too much time sitting, experts may want to expand that recommendation to include sedentary activities, as they appear to have distinct effects on brain health,” said Natan Feter, corresponding author of the study and a postdoctoral fellow in the Human and Evolutionary Biology Program at USC Dornsife.
About this study
In addition to Raichlen and Feter, study authors include Anamika Nanda, Mark Lai, Rand Wilcox and Sarah Hourihan of USC Dornsife. Daniel Aslan of Harvard University. Jayne Fetter of the Federal University of Rio Grande do Sul; M. Katherine Thayer of the University of California, Santa Barbara; Pradyumna Bharadwaj, Madeline Alley, Hyun Sung, Jan Klimentidis, Amit Arora, and Gene Alexander from the University of Arizona; Silvio Maltagliati of Dornsife University of Southern California and University of Brittany South;
This research was supported by National Institutes of Health grants P30AG072980, P30AG019610, R56AG067200, R01AG064587, and R01AG072445 and funding from the State of Arizona, the Arizona Department of Health Services, and the McKnight Brain Research Foundation.
