Research Highlights:
- Increased time on electronic devices or watching TV among children and young adults was associated with higher cardiometabolic disease risk, such as high blood pressure, high cholesterol and insulin resistance, based on data from over 1,000 study participants in Denmark.
- The link between screen time and cardiometabolic risks was strongest among youth who slept fewer hours, suggesting that screen use may harm health by "stealing" time from sleep, researchers said.
- Researchers said the findings underscore the importance of addressing screen habits among young people as a potential way to protect long-term heart and metabolic health.
DALLAS, Aug. 6, 2025 — Children and young adults who spend excessive hours glued to screens and electronic devices may have higher risks for cardiometabolic diseases, such as high blood pressure, high cholesterol and insulin resistance, according to new research published today in the Journal of the American Heart Association, an open-access, peer-reviewed journal of the American Heart Association.
A 2023 scientific statement from the American Heart Association noted that "cardiometabolic risk is accruing at younger and younger ages," and only 29% of American youth, ages 2 to 19 years, had favorable cardiometabolic health based on 2013-2018 data from the National Health and Nutrition Examination Survey.
This analysis of more than 1,000 participants in two studies in Denmark found that increased recreational screen time was significantly associated with higher cardiovascular risks and cardiometabolic risks among children and adolescents.
"Limiting discretionary screen time in childhood and adolescence may protect long-term heart and metabolic health," said study lead author David Horner, M.D., PhD., a researcher at the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) at the University of Copenhagen in Denmark. "Our study provides evidence that this connection starts early and highlights the importance of having balanced daily routines."
Using data from a group of 10-year-olds studied in 2010 and a group of 18-year-olds in 2000 that were part of the Copenhagen Prospective Studies on Asthma in Childhood cohorts, researchers examined the relationship between screen time and cardiometabolic risk factors. Screen time included time spent watching TV, movies, gaming or using phones, tablets or computers for leisure.
Researchers developed a composite score based on a cluster of metabolic syndrome components — waist size, blood pressure, high-density lipoprotein or HDL "good" cholesterol, triglycerides and blood sugar levels – and adjusted for sex and age. The cardiometabolic score reflected a participant's overall risk relative to the study group average (measured in standard deviations): 0 means average risk, and 1 means one standard deviation above average.
The analysis found that each extra hour of screen time increased the cardiometabolic score by about 0.08 standard deviations in the 10-year-olds and 0.13 standard deviations in the 18-year-olds. "This means a child with three extra hours of screen time a day would have roughly a quarter to half a standard-deviation higher risk than their peers," Horner said.
"It's a small change per hour, but when screen time accumulates to three, five or even six hours a day, as we saw in many adolescents, that adds up," he said. "Multiply that across a whole population of children, and you're looking at a meaningful shift in early cardiometabolic risk that could carry into adulthood."
The analysis also found that both sleep duration and sleep timing affected the relationship between screen time and cardiometabolic risk. Both shorter sleep duration and going to sleep later intensified the relationship between screen time and cardiometabolic risk. Children and adolescents who had less sleep showed significantly higher risk associated with the same amount of screen time.
"In childhood, sleep duration not only moderated this relationship but also partially explained it: about 12% of the association between screen time and cardiometabolic risk was mediated through shorter sleep duration," Horner said. "These findings suggest that insufficient sleep may not only magnify the impact of screen time but could be a key pathway linking screen habits to early metabolic changes."
In addition, a machine learning analysis identified a unique metabolic signature in the blood that appeared to be associated with screen time.
"We were able to detect a set of blood-metabolite changes, a 'screen-time fingerprint,' validating the potential biological impact of the screen time behavior," he said. "Using the same metabolomics data, we also assessed whether screen time was linked to predicted cardiovascular risk in adulthood, finding a positive trend in childhood and a significant association in adolescence. This suggests that screen-related metabolic changes may carry early signals of long-term heart health risk.
"Recognizing and discussing screen habits during pediatric appointments could become part of broader lifestyle counseling, much like diet or physical activity," he said. "These results also open the door to using metabolomic signatures as early objective markers of lifestyle risk."
Amanda Marma Perak, M.D., M.S.CI., FAHA, chair of the American Heart Association's Young Hearts Cardiovascular Disease Prevention Committee, who was not involved in this research, said focusing on sleep is a great starting point to change screen time patterns.
"If cutting back on screen time feels difficult, start by moving screentime earlier and focusing on getting into bed earlier and for longer," said Perak, an assistant professor of pediatrics and preventive medicine at Northwestern University Feinberg School of Medicine in Chicago.
Adults can also set an example, she said. "All of us use screens, so it's important to guide kids, teens and young adults to healthy screen use in a way that grows with them. As a parent, you can model healthy screen use – when to put it away, how to use it, how to avoid multitasking. And as kids get a little older, be more explicit, narrating why you put away your devices during dinner or other times together.
"Make sure they know how to entertain and soothe themselves without a screen and can handle being bored! Boredom breeds brilliance and creativity, so don't be bothered when your kids complain they're bored. Loneliness and discomfort will happen throughout life, so those are opportunities to support and mentor your kids in healthy ways to respond that don't involve scrolling."
As an observational study using prospectively collected data, the findings reflect associations rather than proving cause and effect. Moreover, parents of the 10-year-olds and the 18-year-olds reported screen time through questionnaires, which may not accurately reflect the actual time youth spent on screens.
Horner suggested that future research could explore whether limiting screen use in the hours before sleep, when light from screen exposure may disrupt circadian rhythms and disrupt sleep onset, may be an avenue to help reduce cardiometabolic risk.
Study details, background and design:
- The two prospective research groups at COPSAC in Denmark consisted of mother-child pairs, with analysis of data collected at planned clinical visits and study assessments from the birth of the children through age 10 in the 2010 study group and age 18 in the 2000 study group.
- Through questionnaires, parents of children in the 10-year-old group and 18-year-olds detailed the number of hours the young participants spent watching TV or movies, gaming on a console/TV and using phones, tablets or computers for leisure.
- For the 2010 group, the number of hours of screen time was available for 657 children at age 6 and 630 children at age 10. Average screen time was two hours per day at age 6, and 3.2 hours per day at age 10, representing a significant increase over time.
- For the 2000 group of 18-year-olds, screen time was available for 364 individuals. Screen time at 18 years was significantly higher at an average of 6.1 hours per day.
- Sleep was measured by sensors over a 14-day period.
Co-authors, disclosures and funding sources are listed in the manuscript.
