Standing desks — and even bike desks — are a response to a growing body of research showing that a sedentary lifestyle poses many health risks. Regular exercise seems to provide a measure of protection against a variety of problems, both physical and mental, and many results indicate that this doesn’t have to be Olympic-level training. Just 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 will depend on the health conditions involved, there is likely some good news for those reading this, as computer use appears to be somewhat protective against dementia.
Get off your chair
The physical risks associated with inactivity are generally associated with lower cardiovascular health, either directly or through obesity. Even a small amount of exercise seems to be able to limit these effects, although more exercise seems to be even better overall (details vary depending on the study and the exact risk being investigated).
But exercise also seems to improve mental health. It can be an effective therapy for depression and other conditions, and appears to help prevent some of the unfortunate effects of aging. “Exercise and physical activity have shown promise in reducing cognitive decline, structural brain atrophy and dementia risk in older adults,” the authors write, citing work done in other studies.
One of the quirks of some of the studies mentioned in the new one is that several of them watched television for hours as a substitute for the amount of time spent inactive. While that may have been the case a few decades ago, we’ve since greatly diversified our inactivity, with computers and mobile devices offering new ways to feel like you’re doing something without having to do anything.
So the researchers decided to investigate this further and address some related questions. Their study design separated computer use and TV viewing, looking at how each affected the onset of mental problems associated with aging. It also examined whether physical activity could influence the association between sedentary behavior and aging-related problems.
To do this, the researchers used the UK Biobank, a large database that combines anonymized demographic data and health outcomes for hundreds of thousands of UK citizens. For this work, the team excluded people under the age of 60 and focused the work on approximately 75,000 people who had filled in detailed information about their level of activity and leisure time.
Not good, but better
Before we get into the results, a little reminder: The work focused on the influence of sedentary behavior on mental problems. Physical health problems were not examined – it’s possible that something that looks relatively good in this analysis is an overall negative if physical problems are factored in.
That out of the way, what did they see? With age and gender controlled, time spent watching TV was associated with an increased risk of dementia (a hazard ratio of 1.3, meaning they were 1.3 times more likely to be diagnosed with indications of dementia) . Physical activity reduced the risks very slightly. Computer use, on the other hand, reduced the risk by quite a bit, reducing the hazard ratio to 0.8.
The same trend occurred when the researchers divided the group into three and compared high, medium and low TV viewing and computer use. Controlling additional factors such as diet, alcohol consumption, and obesity also did not change the outcome.
While the impact 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. Lots of exercise seems to have a somewhat protective effect, but it’s a minor one.
Overall, the results suggest that we need to separate how we think about the problems associated with sedentary activity. In terms of physical health, each type of inactivity can be roughly equal. But as for mental health issues, how you spend your inactivity matters — some ways of being a couch potato involve passive consumption, and others involve a greater degree of mental activity.
In that sense, the results fit neatly into a large body of studies indicating that staying mentally active can provide some degree of protection against dementia. Things like reading and playing vocabulary games seem to reduce dementia risk overall, and the benefits even seem to increase if reading is done when people are relatively young. So there’s a reason not to be surprised by this overall outcome.
That said, there are still quite a few reasons for caution. Among other potential issues, the researchers note that activity levels were monitored and self-reported at only one point in the participants’ histories, which tends to be less accurate. It’s also important to realize that computer time encompasses a wide variety of activities, some of which are significantly more involved than others. So here’s some work to do. But the next time someone yells at you for wasting time reading Ars, say you’re protecting your sanity.
PNAS2022. DOI: 10.1073/pnas.2206931119 (About DOIs).