People who watch a lot of TV in middle age may have smaller volumes in some areas of the brain associated with thinking and language decades later. American scientists came to this conclusion after analyzing data from more than 1.7 thousand people. However, the researchers did not find a similar connection with sedentary work. The study results were published in the journal Alzheimer's & Dementia.
The researchers used data from the long-term Atherosclerosis Risk in Communities (ARIC) study, funded by the US National Institutes of Health (NIH). Participants, who were between 45 and 64 years old at baseline, were asked to rate how often they watched television and how much time they spent sitting at work.
Participants rated how often they watched TV in five categories: “never,” “rarely,” “sometimes,” “often,” or “very often.” The average age of volunteers at that time was 53 years.
More than 20 years later, the participants underwent magnetic resonance imaging (MRI) of the brain. They found that people who previously reported watching TV “very often” had smaller volumes in some areas.
In particular, differences were observed in areas associated with cognitive control and language, as well as in areas thought to be particularly vulnerable in the early stages of Alzheimer's disease.
In addition, participants who watched television frequently were found to have more white matter hyperintensities. Such changes are visible on MRI and may indicate damage to small blood vessels in the brain. They have also previously been linked to cognitive decline and dementia.
However, sedentary lifestyle alone did not show the same association. Researchers did not find similar negative changes in people who spent a lot of time sitting at work.
This may indicate that not only the duration of sitting is important for brain health, but also what exactly a person is doing at that time.
Watching TV is a predominantly passive cognitive activity: a person mainly receives information without performing complex mental actions. Desk work, on the other hand, can involve texting, performing various tasks, communicating with colleagues, and other activities that involve multiple brain systems.
At the same time, the study results do not prove that watching TV leads to a decrease in brain volume. The work was observational in nature, so scientists were able to establish a connection between the two factors, but not a cause-and-effect relationship.
The researchers took into account participants' age, education level, physical activity, smoking, alcohol consumption, body mass index, diabetes and high blood pressure. However, it is possible that people who watched a lot of TV differed from others in other ways.
The inverse relationship is also possible: early changes in brain function could influence a person’s lifestyle long before the MRI and contribute to the fact that he preferred more passive leisure.
However, the association between frequent television viewing and brain changes persisted even after taking into account the level of physical activity of the participants. Thus, regular exercise in itself did not exclude the relationship identified by the researchers.
The results do not mean that you need to give up TV completely. The authors of the work pay attention primarily to prolonged passive activity and what activities it displaces from everyday life.
Watching films or sports broadcasts may, for example, be part of socializing with friends and family. At the same time, several hours in front of the TV or aimlessly browsing social media can take time away from physical activity, reading, socializing and other activities that require more mental engagement.
For the same reason, different types of screen time cannot be considered the same. An online foreign language lesson or other activity that requires learning and communication engages the brain differently than passively watching TV.
To maintain brain health as you age, experts also recommend maintaining physical activity, monitoring blood pressure, managing chronic diseases, not smoking, limiting alcohol consumption, getting enough sleep and maintaining social connections.
