“Turn off the TV, it will rot your mind!” has been a household refrain for decades. While “rot” may be too strong a term, the researchers note that the general sentiment could have some value.
A study recently published in Alzheimer and Dementia: Journal of the Alzheimer’s Association revealed that those who reported watching television “very often” in middle age later showed reduced volume in brain regions associated with memory, smaller frontal and occipital lobes, and areas of brain white matter damage associated with aging, stroke risk, cognitive decline, and dementia.
For years we have focused on how much people sit. Our findings suggest that we should also pay attention to what they do while sitting.”
David Raichlen, professor of biological sciences and anthropology in the USC Dornsife College of Letters, Arts and Sciences and senior author of the study
The findings were not just due to the sedentary nature of television viewing. 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.
Track changes
Researchers analyzed data from about 1,700 adults, mean age 53, who were enrolled in the Atherosclerosis Risk in Communities (ARIC) Study between 1987 and 1989. ARIC is a long-term study of the US population designed to investigate cardiovascular and brain health.
Participants were asked how often, on a scale ranging from ‘never/rarely’ to ‘very often’, they watched TV in their free time and how much of their working day was spent sitting.
More than two decades later, the participants underwent brain MRIs. Compared to people who reported they “never” or “rarely” watched TV, those who watched TV “very often” showed extensive structural differences in the brain.
The researchers found smaller volumes in areas associated with early signs of Alzheimer’s disease and more volumes of hyperintense white matter, a marker of brain small blood vessel disease associated with cognitive decline and dementia. These participants also had smaller occipital and frontal lobes, areas associated with visual processing and executive function.
The differences remained even when the researchers controlled for factors such as physical activity, diabetes, body mass index, smoking and alcohol use.
It’s worth noting that the researchers relied on self-reported TV consumption data, which may be less accurate than timed viewing. Study participants also did not undergo a baseline MRI. Future research could begin with a baseline MRI to more specifically demonstrate changes over time.
Not all seats are the same
Strikingly, the sedentary component of TV viewing did not appear to be the main driver of 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, suggesting better brain health compared to those who sit to watch TV. This could be due to the intellectually stimulating nature of many jobs, the study authors say.
Men appeared to be particularly vulnerable to these changes. When the MRIs were separated by gender, the researchers found that most of the changes in the brain, from both TV watching and occupational sitting, were seen in men.
Such findings suggest that there is still more research to be done on this complex topic. However, we may eventually see a different approach to health guidance around sedentary activities. Instead of simply directing their patients to move more, for example, doctors might recommend reducing TV time and adding cognitively engaging activities when sitting.
“We often encourage the public not to spend too much time sitting, but experts may want to expand this recommendation to include activities done while sitting, as these appear to have distinct effects on brain health,” says corresponding study author Natan Feter, a postdoctoral scholar in the Human and Evolutionary Biology program at USC Dornsife.
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