Some people say, “Even without knowledge, one must have common sense, and even without common sense, one must watch television frequently.” This statement may serve as an excuse for watching television, but watching too much TV not only wastes time but may also be detrimental to one’s physical and mental health. A recent study has found a link between prolonged TV viewing and a reduction in areas of the brain associated with memory formation, indicating a potential correlation between excessive television watching and an increased risk of dementia.
The University of Southern California released a press release on July 16, stating that for the past few decades, the phrase “Turn off the TV, it’s rotting your brain!” has been echoing in many households.
While the term “rotting” may seem exaggerated, researchers have found that there is some validity behind the notion.
A study conducted by the university revealed that individuals who reported frequent television watching during middle age later exhibited shrinkage in brain regions related to memory, decreased volumes in the frontal and temporal lobes, as well as signs of white matter damage. White matter lesions are indicative of small vessel disease in the brain and are associated with aging, stroke, declining cognitive abilities, and dementia.
The senior author of this study, Professor David Raichlen from the university’s Departments of Biological Sciences and Anthropology, explained, “We have focused on the amount of time people spend sitting for years. Our study suggests that what people do while sitting may also be important.”
The study found that other types of sedentary activities did not show the same correlations, indicating that the activities individuals engage in while sedentary may be more significant than previously thought.
In this research, approximately 1,700 adults’ data were analyzed, considering both their frequency of television watching during leisure time (ranging from “never” to “very frequent”) and the duration of sedentary behaviors during workdays.
Twenty years later, these participants underwent brain magnetic resonance imaging (MRI) scans. Compared to those who reported “never” or “rarely” watching television, individuals who watched television “very frequently” showed extensive structural differences in various brain regions.
Researchers discovered that individuals who watched television regularly exhibited smaller brain volumes in regions associated with early signs of Alzheimer’s disease, along with white matter lesions. Additionally, these participants had smaller volumes in the temporal and frontal lobes, which are respectively linked to visual processing and executive functions.
Even after controlling for factors such as physical activity, diabetes, body mass index (BMI), smoking, and alcohol consumption, these differences persisted.
It is important to note that the data related to television viewing time were based on participants’ self-reports, which may not be as accurate as precise time recordings. Furthermore, these participants did not undergo MRI scans prior to the study. Future research could start with MRI scans to more accurately demonstrate changes over time.
Researchers noted that the sedentary state of watching television did not seem to be the primary factor leading to these changes.
Compared to individuals who spent prolonged periods watching television, those who had longer sedentary time at work exhibited larger volumes in the temporal and frontal lobes and less white matter lesions, indicating better brain health. Researchers suggest that this might be attributed to the intellectual stimulation inherent in many occupations that require prolonged sitting.
Interestingly, men seemed to be particularly susceptible to these changes. When researchers analyzed the MRI results by gender, they found that brain changes due to either television watching or prolonged sitting at work primarily occurred in men.
Researchers speculate that future health guidelines for sedentary behavior may change. Instead of simply recommending more physical activity, doctors may advise individuals to reduce their TV viewing time and engage in more mentally stimulating activities when unable to avoid sitting.
The findings of this study were published on July 10 in the journal “Alzheimer’s and Dementia.”
A previous study conducted by the University of Queensland in Australia also found that not all sedentary activities have the same impact on brain health. Sedentary behaviors like watching television may lead to brain atrophy or cognitive decline.
Researchers suggest that when sedentary, choosing activities that stimulate the brain might be preferable, such as reading, playing card games, puzzles, using computers, and driving.
（Extended reading: Study: Different types of sedentary activities have varying effects on brain health）