Published on Wednesday, August 6, 2025, a Danish cohort study warned that excessive screen time during childhood and adolescence increased early cardiometabolic risk. The paper, released in the Journal of the American Heart Association and led by David Horner at the University of Copenhagen, drew its data from 1,287 participants followed through the COPSAC project since birth.
Researchers recorded recreational screen use at ages six, ten, and 18, then matched those reports with waist circumference, blood pressure, HDL cholesterol, triglycerides, and fasting glucose to build a cardiometabolic risk index. Six-year-olds averaged two hours of daily screen time, ten-year-olds about three hours, and 18-year-olds six hours. Each extra daily hour raised the risk index by 0.08 standard deviations at age ten and by 0.13 at age 18, showing a steeper gradient in late adolescence.
“The individual correlation was not very high, and the analysis remained observational, so causality cannot be proven,” said Renate Oberhoffer, Chair of Preventive Pediatrics at the Technical University of Munich. Still, “the effect size per additional hour is very relevant at population scale,” said epidemiologist Sebastian Freilinger, according to Die Welt.
“A child exposed to screens for an additional three hours a day will face a 25–50 percent higher risk than peers,” said Horner, according to Stern. He cautioned that, multiplied across an entire population, the burden could reshape early-life health profiles.
Sleep appeared to mediate part of the link. About 12 percent of the screen-time risk traced back to insufficient sleep. “Lack of sleep may amplify the impact of screen time and act as a pathway to early metabolic change,” said Horner, according to Correio Braziliense.
Using artificial-intelligence tools, the team identified a blood-borne “digital fingerprint of screen time” that correlated with device use. “That fingerprint could become an early-warning tool before clinical symptoms appear,” Horner said.
Prior U.S. data showed only 29 percent of youths aged two to nineteen had favorable cardiometabolic health. “If reducing screen time is difficult, move it earlier in the day and focus on longer, earlier sleep,” advised Amanda Marma Perak, chair of the American Heart Association’s Council on Cardiovascular Disease in the Young.
Public-health bodies have started drawing stricter lines. Belgium’s Sciensano recommended a maximum of two daily recreational screen hours for five- to 17-year-olds and one hour for children aged three and four. More than half of U.S. states have limited mobile-phone use in schools, and the Surgeon General urged households to create technology-free zones.
Horner emphasized that the study did not call for removing tablets from homes, but for managing their use. “Limiting discretionary screen time during childhood and adolescence may protect long-term cardiac and metabolic health,” he said. He suggested board games, shared reading, or cooking together as screen-free alternatives that keep families connected while giving young hearts a rest.
Produced with the assistance of a news-analysis system.