Spending too much time on smartphones and other electronic devices could harm the heart health of children and young adults, according to a new study from Danish researchers. The findings, published in the Journal of the American Heart Association, suggest that screen time may increase the risk of high blood pressure, high cholesterol, and insulin resistance, particularly in those who get less sleep.
The study, led by Dr. David Horner of the University of Copenhagen, analysed data from over 1,000 children and teenagers in Denmark. Researchers found that each additional hour of screen time was associated with a higher cardiometabolic risk score, which took into account waist size, blood pressure, and other factors. For a child with three extra hours of screen time a day, the risk was roughly a quarter to half a standard deviation higher than their peers.
Sleep duration and timing played a crucial role. The researchers noted that about 12% of the association between screen time and cardiometabolic risk was mediated by shorter sleep duration. “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,” said Dr. Horner.
The study also used machine learning to identify a “screen-time fingerprint” in the blood, indicating biological changes linked to screen use. This fingerprint was associated with predicted cardiovascular risk in adulthood, suggesting that screen-related metabolic changes may signal long-term heart health risks.
In the United States, the problem is widespread. A 2023 American Heart Association statement found that only 29% of young people aged two to 29 had good cardiometabolic health, while U.S. children aged eight to 18 spend an average of 7.5 hours per day on screens, according to the American Academy of Child and Adolescent Psychiatry.
Experts advise transitioning away from screens gradually. Dr. Amanda Perak, chair of the American Heart Association’s Young Hearts Cardiovascular Disease Prevention Committee, suggested: “If cutting back on screen time feels difficult, start by moving screentime earlier and focusing on getting into bed earlier and for longer.”
