An image of a person in front of a TV.

Computers vs. TV: Which Is Less Likely to Promote Dementia?

Standing desks—and even bicycle desks—are a response to a growing body of research showing that a sedentary lifestyle carries many health risks. Regular physical activity appears to provide some protection against a variety of physical and mental problems, and many results suggest that this is not necessarily Olympic-level training. Walking around the apartment a few times a day seems to help.

Now, a team of researchers has looked at the opposite question: Are all forms of inactivity equal? The answer is probably not. While the details depend on the health issues involved, there may be some good news for those reading this, as computer use appears to have some protective effect against dementia.

leave your chair

Physical risks associated with inactivity are often associated with lower cardiovascular health, either directly or through obesity. Even small amounts of physical activity seem to limit these effects, although increased exercise generally seems to be better (the details depend on the study and the exact risks being examined).

But exercise also appears to improve mental health. It can be an effective treatment for depression and other ailments, and appears to help avoid some of the unfortunate effects of aging. “Exercise and physical activity have shown promise in reducing the risk of cognitive decline, structural brain atrophy, and dementia in older adults,” the authors wrote, citing work done in other studies.

One of the oddities of some of the studies mentioned in the new study is that some of them used TV-watching time instead of inactive time. While this may have been true decades ago, we’ve greatly diversified our inactivity, with computers and mobile devices offering new sensations like you’re doing something without needing to do anything.

Therefore, the researchers decided to study this in more detail and address some related questions. Their study design separates computer use and television viewing, and examines how both affect the development of psychological problems associated with aging. It also examined whether physical activity affects the association between sedentary behavior and aging-related problems.

To do this, the researchers drew on the UK Biobank, a large database that combines anonymous demographic data and health outcomes of hundreds of thousands of UK citizens. For this work, the team excluded people under the age of 60 and focused on the roughly 75,000 people who filled out details about their activity levels and leisure activities.

bad but better

A small reminder before we get into the results: this work focuses on the effects of sedentary behavior on psychological problems. Physical health issues are not checked – once physical issues are factored in, what looks relatively good in this analysis may turn out to be overall negative.

No problem, what did they see? Time spent watching TV was associated with an increased risk of dementia when controlled for age and sex (hazard ratio was 1.3, meaning they were 1.3 times more likely to be diagnosed with signs of dementia). Physical activity reduced the risk very slightly. In contrast, using a computer reduced the risk by a lot, reducing the hazard ratio to 0.8.

The same trend remained the same when the researchers divided the group into three equal parts and compared high, moderate and low TV viewing and computer use. Controlling for other factors such as diet, alcohol use and obesity also did not alter the results.

Although the effect of physical activity was small, the researchers tested whether it could offset some of the problems associated with high TV viewing or low computer use. High-intensity exercise appears to have some protective effect, but it is secondary.

mental reserve

Overall, the results suggest that we need to differentiate how we view issues related to sedentary activities. In terms of physical fitness, any type of inactivity can be about the same. But when it comes to mental matters, how you spend your inactivity matters — some ways of being a couch potato involve passive consumption, while others involve a greater degree of mental activity.

In this sense, these results are in perfect agreement with a large body of research showing that staying mentally active can protect against dementia to some extent. Things like reading and playing vocabulary games seem to generally reduce dementia risk, and these benefits seem to increase even when reading occurs when people are relatively young. Therefore, we are reasonably not surprised by this overall result.

Still, there are quite a few reasons to be cautious. Among other potential problems, the researchers noted that activity levels were only examined at one point in the participant’s history and were self-reported, which tended to be less accurate. It is also important to realize that computer time will include a wide range of activities, some of which are much more numerous than others. So there is still some work to be done here. But the next time someone yells at you for wasting time reading Ars, you can tell them you’re protecting your mental health.

NASA2022. DOI: 10.1073/pnas.2206931119 (on DOI).

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