Alarming study:

More time in front of a screen makes people more short-sighted

Children are particularly affected, with myopia apparently occurring earlier and more frequently around the world.

(Bild: Seventyfour – stock.adobe.com)

The incidence of short-sightedness (myopia) is increasing rapidly worldwide. The effect of "screen time" is "dose-dependent", as a South Korean-Irish team of scientists has now discovered: One hour more time in front of a screen increases the risk by 21 percent.

Eye specialist Ahnul Ha (Jeju University Hospital/South Korea) and her co-authors published the results of their analysis of 45 corresponding scientific studies with 335,524 test subjects online a few days ago in JAMA Network Open of the American Medical Association (AMA) (DOI:10.1001/jamanetworkopen.2024.60026 ).

Soon to affect half of the world's population

"Myopia prevalence (frequency of myopia in the population; note) is increasing. Forecasts predict that almost half of the world's population will be affected by 2050. This increase is associated with an earlier onset, faster progression and greater severity of myopia with eventual stabilization. It also points to a future increase in the global burden of myopia-related sight-threatening diseases such as macular degeneration, retinal detachment and glaucoma," the experts wrote.

Earlier and more frequent
The main causes of myopia appear to lie in modern lifestyles and environmental factors: More and more time is spent on near-vision activities, less and less time outdoors. Children are particularly affected, with myopia apparently occurring earlier and more frequently worldwide. The team of authors of the scientific analysis: "As children are switching to smart devices earlier and spending more time in front of digital screens, there is an urgent need to better understand the relationship between digital screen time and myopia."

The experts led by eye specialist Ahnul Ha (Jeju University Hospital/South Korea) therefore analyzed the data from 45 scientific studies published in prestigious peer-reviewed journals up to November 25 last year. They used 45 publications that investigated the relationship between the use of digital screen devices (e.g. smartphones, tablets, game consoles, computers or televisions) and myopia-related consequences (e.g. myopia and the speed of its progression). The mean age of the 335,524 test subjects from the studies was 9.3 years. Short-sightedness usually occurs in childhood.

Risk doubles with four hours of "screen time"
The main result: with an additional hour of screen time, the risk of becoming short-sighted increased by 21 percent. While one hour of "screen time" per day had hardly any effect, the frequency of myopia increased by up to 97 percent, i.e. doubled, up to four hours a day in front of the screen of the various devices. Only then did the dose-response relationship flatten out. One hour more in front of a screen also led to a 54 percent faster development of short-sightedness.

Screen time has the strongest effect on preschool children. "In a subgroup analysis conducted according to the age of the study participants, a statistically significant correlation was observed across all age groups (...)", the scientists wrote. In the age group of two to seven-year-olds, the frequency of myopia increased by 42 percent with one hour more in front of screen-equipped electronic devices, only to increase by 12 percent thereafter (eight to 18 years) and by 16 percent in the age group above that.

The more screens, the worse
The use of multiple electronic devices appears to be particularly conducive to the occurrence of myopia. "According to the subgroup analysis, which was based on whether screen devices were evaluated individually or in combination, the probability of myopia was significantly higher when the devices were analyzed in combination(risk increase of 28 percent; note) than when analyzing individual devices (...)," the experts found.

Remarkably, the correlation remained insignificant for screen time of up to one hour per day, which could indicate a potential safety threshold, the scientists believe. The future promises little improvement: the global penetration of smartphones alone has risen from 21.6 percent in 2014 to 69 percent in 2023. "Many two-year-olds spend up to two hours a day using such devices," according to the paper published in JAMA Network Open by the American Medical Association.