Children and teenagers who spend many hours on televisions, phones, tablets, computers, or gaming systems face a higher risk of cardiometabolic problems, such as elevated blood pressure, unfavourable cholesterol levels, and insulin resistance, according to an analysis of more than 1,000 participants in Denmark.
The study, published in the Journal of the American Heart Association, found that every additional hour of recreational screen time was linked with an increase of about 0.08 standard deviations in cardiometabolic risk scores for 10-year-olds and 0.13 standard deviations for 18-year-olds.
The association between screen time and cardiometabolic risks was strongest in youth who slept fewer hours, suggesting that screen use may harm health by displacing time from sleep. About 12 per cent of the association between screen time and cardiometabolic risk was mediated through shorter sleep duration in children.
“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 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.”
Tracking phones, tablets and computers
The team analysed two groups: one of 10-year-olds followed in 2010 and one of 18-year-olds followed in 2000. Screen time included watching television and films, gaming and time on phones, tablets or computers for fun.
Researchers created a composite cardiometabolic score based on multiple components of metabolic syndrome, including waist size, blood pressure, HDL cholesterol, triglycerides and blood sugar levels.
Average screen time was two hours per day at age six, 3.2 hours per day at age 10, and 6.1 hours per day at age 18.
“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,” said Horner. “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.”
In a machine learning analysis, investigators identified a distinctive pattern of blood metabolites that appeared to correlate with screen time—a “screen-time fingerprint” validating the potential biological impact of the behaviour.
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 the 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 paediatrics and preventive medicine at Northwestern University Feinberg School of Medicine in Chicago.
