Spending a lot of time watching television might be relaxing after a long day, but it also leads to brain shrinkage and lower cognitive function.

At a recent American Heart Association (AHA) virtual conference, researchers involved in three new studies presented shocking evidence on the impact of television viewing on the brain. Let’s take a closer look…

Cognitive Function Sinks 6.9 Percent 

The first study included 10,700 men and women with an average age of 59 when the study began. The study involved five visits during the 26 years from 1987 to 2013. During visits one and three, which covered the first six years of the study, the volunteers reported their viewing habits to the interviewers.

Visits four and five covered 15 years and included tests of working memory, language and executive function and processing speed.

For those who spent the most time in front of the television, findings were concerning. Researchers found that irrespective of the amount of physical activity and exercise the participants engaged in, compared to those who said they never or seldom watched TV, those who watched sometimes or often to very often had a 6.9 percent greater decline in cognitive function over 15 years.

On the plus side, there was no significant change in dementia risk. How do researchers explain the loss in cognitive function? Let’s take a look at the results of the second study…

Gray Matter is Lost 

The second study was linked to the first but included a different subset of 1,601 participants with an average age of 76.

Each participant reported their viewing habits at visits one and three, the same as before, but instead of cognitive tests during visit five they underwent MRI brain scans.

In this study, compared to the never or rarely ever viewers, the moderate or high TV watchers had reduced volumes of deep gray matter more than a decade later, indicating greater brain atrophy. This will likely translate to diminished cognitive abilities.

As with the first group, self-reported physical activity and exercise habits had no effect on the findings.

Columbia University’s Priya Palta, lead author of the first study, commented on both studies, saying, “Our findings suggest that the amount of television viewing, a type of sedentary behavior, may be related to cognitive decline and imaging markers of brain health. Therefore, reducing sedentary behaviors, such as television viewing, may be an important lifestyle modification target to support optimal brain health.”

The Young Have Older Brains 

For the third TV viewing study reported at the AHA conference, 599 younger participants were enrolled whose average age was 30 when the investigation began.

Participants made five visits over 20 years during which researchers asked them the average number of hours per day they spent watching television over the previous 12 months. At the end of the study each participant’s brain was scanned.

Researchers’ findings were in line with the first two studies. But the brain scans revealed something new and shocking: Every additional hour of viewing was linked to a 0.5 percent reduction in gray matter volume. This reduction is much the same as seen in people who are 20 years older!

Consistent with the other studies, physical activity and exercise didn’t change the outcome.

What You Do While Sitting is Key 

These studies back up previous findings that show even working out at the gym won’t compensate for extended periods sitting down each day.

However, unlike Dr. Palta, lead author of the third study, Ryan Dougherty, from Johns Hopkins Bloomberg School of public health, distinguished between types of sedentary behavior.

Dr. Dougherty said that television is non-stimulating and risks cognitive decline, whereas other sedentary activity, like playing computer or board games, can stimulate the brain, maintain cognition and reduce the likelihood of dementia. So, in his view, TV stands out from other forms of behavior that involve a lot of time sitting down.

Mitchell Elkind, President of the AHA, summed up the findings by saying, “These are interesting correlations among television viewing, cognitive decline and brain structure. Television viewing is just one type of sedentary behavior yet it’s very easy to modify and could make a big difference in maintaining and improving brain health.”

My Takeaway 

I’ve never been a big fan of the television. I’d much prefer to read a book or ocassionally watch a movie. This research just proves true what I’ve always believed: television should be enjoyed in moderation.

It seems to me there are some oddities about the way the researchers interpreted their results. I would have checked to see if heavy TV watching correlates with lower intelligence and education. It’s well known that these are risk factors for cognitive decline. The researchers seem to have focused on television as reducing physical activity, when it’s the lack of mental challenge that might make heavy watching so damaging.


  1. https://newsroom.heart.org/news/moderate-to-high-tv-viewing-in-midlife-linked-to-later-cognitive-
    and-brain-health-decline?preview=565c

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