Would you reduce screen time if it accelerated aging? Then you wanna read this ...

Inside every human cell, our chromosomes are protected by tiny caps called telomeres. These structures shorten with age, which inevitably leads to DNA damage, cell death, and the breakdown of tissues over time.

Scientists have found that the length of telomeres in white blood cells can serve as a marker of biological aging.

So yes, we know that smoking shortens the telomere, too little sleep, too much of other stuff. But what if the time you spend in front of a screen for pure leisure reduces your lifespan?

And not because you work out less while watching The Kardashians, or because Chips with sea salt taste better with House of Cards in the background.

No, what if the tendency to look a lot at the screen for leisure, isolated, affects the length of your telomere, a.k.a. the time you have left on the planet (at least above ground).

Would you change habits? Could you?

Sedentary behavior
To understand how lifestyle might influence this aging marker, a research team focused on a behavior that has become more widespread in the digital age—leisure screen time.

This refers to time spent watching television or using computers and mobile devices for non-work and non-school purposes. Earlier studies have linked sedentary behavior to poorer health outcomes, such as a higher risk of heart disease and cancer.

However, the connection between screen time and biological aging remains unclear, with conflicting findings in past research.

To reduce potential bias, this study used a genetic technique called Mendelian randomization to explore whether a person’s genetic predisposition to high screen time could actually cause faster aging.

(YES - that´s right - you can be genetically predisposed to sedentary behavior. Made so much sense to me)

From genes to screens: A deep dive into the data
The researchers collected data from over 7,000 adults participating in a major U.S. health survey conducted between 1999 and 2002. All participants underwent physical exams, lab tests, and questionnaires.

Screen time was measured through interviews, while muscle mass was assessed using full-body scans. Telomere length was measured from blood samples and expressed as a ratio compared to standard DNA. The frailty index was calculated based on 49 variables, including cognitive function, chronic illnesses, mood, physical performance, and lab values.

The researchers wanted to isolate the effect of screen time on aging. So they included info from the participants, that is known to affect health, such as age, body weight, smoking, income, education, and physical activity.

They also added genetic data from the participants and compared it to large international genome databases. These databases covered hundreds of thousands of people of European ancestry and included genetic variants linked to screen time, physical activity, telomere length, lean mass, and frailty.

Only the strongest genetic markers were used. Several statistical models were applied to test the strength of the connections, including methods that adjust for physical activity to see if screen time alone had a direct effect on aging.

What the numbers revealed about screen time and aging
The average participant in the study was around 46 years old, with most reporting more than one hour of screen leisure time daily. Well, fewer than one-third limited themselves to one hour or less.

The results showed that people who spent more time on screens had shorter telomeres, less muscle mass, and higher frailty scores.

These associations remained even after adjusting for other lifestyle factors. For every additional hour of screen time per day, participants had a measurable drop in telomere length, a loss of muscle mass, and an increase in frailty.

More specifically, five or more hours of daily screen time was linked to noticeable reductions in muscle mass and increased signs of biological aging. Interestingly, the effects were stronger in men than women and in people over 50 compared to younger individuals.

Beyond the survey data, genetic analyses supported a direct causal link between leisure screen time and biological aging. The relationship remained even when controlling for how physically active someone was.

This suggests that screen time contributes to aging through mechanisms other than simply replacing exercise.

Researchers also identified dozens of genes shared between screen time and aging traits. Four core genes stood out as being involved in all three outcomes: telomere shortening, muscle loss, and increased frailty.

The biology behind how binge-watching ages you ..
To explore how screen time might affect aging at the molecular level, the team identified hundreds of genes that were either more or less present in connection with screen time and length of the telomere (aka aging).

These genes were involved in several important pathways. For example, screen time appeared to affect how cells respond to damaged proteins, how proteins are broken down in the body, and how the immune system functions.

Many of the identified pathways were linked to oxidative stress, a process where unstable molecules called free radicals damage cells. Chronic low-grade inflammation was also a common feature, as was a disruption in protein balance, both of which are known contributors to aging.

Muscle loss may be partly due to reduced activity of enzymes that help break down fats in muscle tissue. Another possible reason is poor diet, as high screen time is often associated with more sugary snacks and soft drinks, which can also contribute to oxidative stress and telomere shortening.

Furthermore, when cells accumulate damage and stop dividing, they become "senescent". These aged cells secrete harmful molecules that promote inflammation and tissue breakdown. Screen time, through multiple pathways, may increase the buildup of these senescent cells.

Why physical activity may not fully offset screen time
A key question in the study was whether the negative effects of screen time could be neutralized by physical activity. After all, regular exercise is known to help maintain telomere length and muscle mass.

However, this study found that even after adjusting for physical activity, high screen time still predicted faster aging. This suggests that the harmful effects of screen time may operate through different biological channels (kind of like why a salad does not neutralize an ice cream).

For instance, physical activity helps reduce inflammation and supports healthy cell function, but prolonged screen exposure may overwhelm these benefits by promoting metabolic changes that lead to muscle atrophy.

Sedentary behaviors lower the activity of fat-processing enzymes in muscles, which can reduce energy use and encourage fat storage. Add poor dietary habits and disrupted protein metabolism into the mix, and the aging process may speed up even more.

This study presents compelling genetic and physiological evidence that screen-based sedentary behavior is not just a passive byproduct of modern life but a potential driver of aging itself.

While physical activity remains important, the findings suggest that reducing screen time may be just as critical for preserving telomere length, muscle mass, and overall vitality as we age.

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About the paper that inspired:

First Author: Jie Wen, China
Published: Neurotherapeutics, May 2025
Link to paper: https://www.sciencedirect.com/science/article/pii/S1878747925000777