The digital device dilemma: What type of screen time can cause dementia?

By Jules Murtha | Medically reviewed by Dani Cabral, MD
Published July 21, 2023

Key Takeaways

  • Research shows that watching TV poses risks to cognitive functioning in adults of any age. Use of computers, on the other hand, does not.

  • Brain-training apps have the potential to improve processing speed and overall cognitive performance in older adults aged 60 to 80.

  • Evidence shows that passive screen time may increase risk of dementia and Alzheimer’s disease, while active screen time may reduce that risk. In order to improve patient health outcomes, physicians can discuss the difference with their patients.

On average, Americans reportedly watch between 2 and 3 hours of television each day. Although an enjoyable experience for many, watching TV is linked with an increased risk of cognitive decline—including dementia—according to a 2023 article from Harvard Health Publishing.[]

If time in front of a TV has a negative impact on cognitive performance, how might time in front of a computer or smartphone affect brain health? Physicians can inform patients about the varying effects of passive and active screen time in order to encourage healthier habits.

Television is out, computers are in

It’s an unfortunate reality that TV hurts brain health. But, this isn’t the case for all digital devices.

One 2022 study published by PNAS looked at the potential link between leisure-time sedentary behaviors (SBs) and risk of all-cause dementia.[] Researchers included 146,651 participants aged 60 and older (none with a dementia diagnosis) from the UK Biobank. The participants self-reported their leisure-time SBs, categorized as either watching television or using a computer.

Over the course of about 11.87 years, 3,507 total participants were diagnosed with all-cause dementia.

The analysis revealed that the participants who watched TV were at a higher risk of developing dementia (HR = 1.24; 95% CI = 1.15 to 1.32), while those who spent time using a computer were at a decreased risk (HR = 0.85; 95% CI = 0.81 to 0.90). 

The most meaningful finding of the study was that participants who watched the most television daily—more than 4 hours—were 24% more likely to develop dementia.

According to the authors, these conclusions may mean that sitting isn’t the inherently harmful aspect of SBs: “Our results help clarify associations of SB with brain health and suggest that it is not time spent sitting per se but the type or context of leisure-time SB that is associated with dementia risk,” they wrote.

Danielle Cabral, MD, MDLinx medical advisory board member and neurologist/psychiatrist specializing in Alzheimer’s disease, points out some confounding factors of the study. “We know beta amyloid plaques and tau neurofibrillary tangles begin building up years before Alzheimer’s disease (AD) [and] dementia symptoms, so it is possible that the participants with more passive SBs already had these AD brain changes occurring, which contributed to choosing less challenging/stimulating SBs.”

As well, Dr. Cabral says it is important to note the TV watchers may have had other contributing factors toward cognitive impairment, such as sleep or mood disorders and the use of certain medications, among others.

While these confounding factors may only lead to more questions, the study results could be a significant stepping stone in dementia prevention.

"Perhaps with more supporting evidence, more than 4 hours per day spent TV viewing could be considered a warning sign of future dementia symptoms, and a trigger to healthcare professionals and families to conduct further evaluation."

Danielle Cabral, MD

Computer use as a cognitively active pursuit

The UK Biobank study wouldn’t be the first to shed light on the potential benefits that cognitively active screen time may provide to patients.

Another study, published by the American Journal of Epidemiology, found that watching TV and driving were both linked with the risk of cognitive decline, while computer-use time was “inversely associated with the odds of having cognitive decline at follow-up across most outcomes,” the authors wrote.[]

In other words, computer use was positively linked with cognitive performance across the board.

So, no need to ditch your computers—or your phones, for that matter—in the attempt to ward off cognitive decline.

How brain-training apps fit into the puzzle

Smartphones must be included in the discussion of what role digital devices play in cognitive decline. These handy little devices that exist in most peoples’ pockets may have a better influence on brain health than you think.

A 2021 study published by Scientific Reports looked at the benefits of cognitive mobile games (CMG) among 12,000 adults aged 60 to 80.[]

Researchers analyzed the processing speed and game scores available across 100 sessions.

What they found was an interaction between the training session and the participant’s age. The authors wrote: “As for the initial scores, we observed an interesting linear trend between age and session, indicating that all participants improved in all CMG but that the progress was slower in older participants (p < 0.001 for the 7 CMG).”

Changes in participant processing speed varied depending on the game.

For example, researchers noted a statistically significant increase in processing speed among all participants who played the games Square Numbers, Unique, and Rush Back.

Only younger participants who played Must Sort, however, showed a slight increase in processing speed; those aged 70 and older showed a slight decrease.

The authors elaborate on the clinical significance of the overall results.

“Users who trained with the games improved regardless of age in terms of scores and processing speed throughout the 100 sessions,” they wrote.

"[This suggests] that old and very old adults can improve their cognitive performance using CMG in real-life use."

Authors, Scientific Reports

While these results trend positive, more research is needed to prove that CMG can actually ward off cognitive decline in older adults. “The jury is still out on whether brain games can prevent dementia,” says Dr. Cabral. “And there remains no convincing evidence that they can.”

Regardless, smartphones may give older adults the opportunity to sharpen their minds through the use of brain-training apps. This is just one form of active screen time that, cognitively speaking, kicks TV to the curb.

What this means for you

Passive screen time, like watching TV, can be detrimental to cognitive health. In fact, those who watch TV are at a higher risk of developing all-cause dementia. Cognitively active screen time, on the other hand, may reduce the risk of neurodegenerative disease. In order to help maintain or improve cognitive function among patients, you may encourage them to watch less TV and instead turn to their computers or brain-training apps. 

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