Excessive screen use by children and adolescents can affect their heart health.

Spending long hours glued to screens during childhood and adolescence could contribute to the development of metabolic and cardiovascular problems later in life . This is suggested by a study published in the Journal of the American Heart Association , which analyzed data from two groups of children and adolescents followed since birth in Denmark.

The study concludes that leisure time spent on devices is associated with increased cardiometabolic risk from an early age. This includes factors such as hypertension, high cholesterol, insulin resistance, and a larger waist circumference.

“Limiting screen time during childhood and adolescence may protect long-term heart and metabolic health,” says David Horner, a researcher at the COPSAC center at the University of Copenhagen and leader of the study. “Our study provides evidence that this relationship begins very early and underscores the importance of having balanced daily routines.”

Horner told SINC that his interest in this research stems from a broad focus on lifestyle factors in the early stages of life, such as diet, sleep, and physical activity , which can influence long-term health.

“During my clinical work with children, I observed how cardiometabolic diseases often stem from patterns formed during childhood. Screen time stood out as a modern, widespread behavior that could influence health, not only through inactivity, but also through other factors such as stress or sleep disturbance,” she explains.

This study, he continues, “allowed us to examine these relationships with detailed, long-term data from two well-characterized Danish birth cohorts.”

The research was based on data from more than 1,000 children and adolescents from these two cohorts and followed for years. The team analyzed self-reported screen time at ages 6 and 10 in one group, and at age 18 in the other. The daily average increased from 2 to 3.2 hours between ages 6 and 10, and reached 6.1 hours at age 18.

The authors developed a composite score from five parameters: waist circumference, blood pressure, HDL cholesterol, triglycerides, and glucose. Each additional hour of screen time was associated with an increased risk : 0.08 standard deviations in 10-year-old children and 0.13 in adolescents. “This means that a child with three more hours per day would have a risk between a quarter and a half standard deviation higher than their peers,” Horner explains.

"It's a small change per hour, but when the total time reaches three, five, or even six hours a day, as we saw in many adolescents, the effect accumulates," he warns. "Multiplied by an entire child population, it represents a significant shift in cardiometabolic risk that could persist into adulthood."

The study also explored the mechanisms that could explain this relationship, and one of them was sleep. The analyses showed that both the duration and timing of sleep influenced the effect of screen time: those who slept fewer hours or went to bed later were at greater risk.

“In childhood, sleep duration not only moderated this relationship, but also explained part of the link: approximately 12% of the association between screen time and cardiometabolic risk was due to shorter sleep ,” notes the Danish researcher.

In addition, the team identified a specific set of metabolites in the blood that were associated with electronic device use, a kind of metabolic fingerprint.

“We found a distinctive pattern of metabolites that was consistently associated with increased screen use in both childhood and adolescence,” Horner says. “This suggests that this habit may leave a measurable biological trace, reflecting changes in metabolism even before symptoms of disease appear.”

According to the author, these fingerprints could become early warning tools in pediatric care in the future to detect children at risk early , before more obvious clinical factors become apparent.

"We are also using these data to evaluate whether there is an association between screen time and future cardiovascular risk: the results have shown an upward trend in childhood and a significant association in adolescence," he says.

As for recommendations, Horner suggests focusing on sleep as a starting point for improving digital habits. “One practical approach would be to protect bedtime, move screen use earlier in the day, and reserve device-free times, such as meals, to promote balance,” she says. “Small, consistent changes can translate into cumulative health benefits.”

The team currently tracks children from ages 10 to 13, and unlike earlier analyses, it uses objective data obtained directly from their phones to more accurately understand their usage patterns.

“This long-term perspective is essential to moving from observing associations to identifying effective preventive strategies,” Horner notes.

Although this is an observational study, the results add to growing evidence that digital behaviors can influence metabolic health. The American Heart Association already warned in 2023 that only 29% of American youth between the ages of 2 and 19 had favorable cardiometabolic health , and that the risk is increasing at increasingly younger ages. This new study sheds light on one of the factors that may be behind that trend.