A study published in Scientific Reports evaluated more than 3,600 people over age 50. 

It found that those watching more than 3.5 hours of TV a day saw an 8% to 10% decline in their verbal memory after six years. Those who watched less than 2.5 hours a day saw only a 4% to 5% decline.

And the more TV they watched, the greater the declines. Those people with better cognition when the study started saw bigger drops. 

Of course, a range of factors can contribute to the strength of your brain as you age. 

“They are really looking at an association,” says Rebecca Edelmayer, director of scientific engagement for the Alzheimer’s Association. “I don’t think at this point we can draw the conclusion that only this specific behavior dulls verbal memory. Several mechanisms could be in play that this manuscript doesn’t take into account.”

Still, researchers found a link between TV viewing and declines in memory even after accounting for cognitive levels at the start of the study, physical activity, demographic factors, health-related factors, and sedentary behavior. 

What’s behind the link?

It’s not the sedentary nature of TV viewing that is behind the cognitive decline found in the study. Other sedentary activities, like using the Internet, are linked with a reduced risk of dementia

It’s possible that the combination of TV’s fast-paced sights and sounds plus the passive nature of TV viewing is causing the declines. Playing video games and using the Internet don’t lead to similar drops, the study points out. 

The study also notes that the stressful content of violent or suspenseful TV shows might be behind the declines, since stress is linked with cognitive impairment.

Or, it could be that TV viewing displaces other, more brain-health-boosting activities like playing board games, reading, visiting museums, or attending concerts. 

“We need more research into understanding the mechanisms behind television watching. Is it television watching itself? Or the behaviors of sitting still and not moving, or not engaging with family and friends and having conversations? It’s hard to say at this point,” Edelmayer says. W

More research needed

There are questions this study didn’t address:

  • Do different types of TV shows affect cognitive decline differently? (Is there a difference if you watch the Khardashians or nature documentaries?) The study asked people how much TV they watched, not what types of shows they watched.

    Edelmayer points out that challenging your brain can help keep it strong. She speculates that shows that teach you something new might be better than those you watch passively. 
  • Is watching TV a risk factor for dementia? Researchers have wondered since at least 1993 if there’s a link between excessive TV viewing and dementia, and some smaller studies have found links. 
  • How much is too much? This study found declines beginning at 3.5 hours a day. While the American Academy of Pediatrics makes recommendations for screen time and children, there aren’t any comparable recommendations for adults.