Too much screen time increases risk of heart attack or stroke: study

By Stephen Beech

Young people who spend hours on end glued to screens are increasing their risk of a heart attack or stroke, warns new research.

Excessive time spent on phones, gaming consoles or watching telly among children and young adults was also associated with increased danger of high blood pressure, high cholesterol and insulin resistance, say scientists.

The findings, published in the Journal of the American Heart Association, were based on data from more than 1,000 people who participated in two studies in Denmark.

Researchers said the link between screen time and cardiometabolic risks was strongest among youngsters who slept fewer hours, suggesting that screen use may harm health by “stealing” sleep time.

Analysis of figures from the Danish studies found that increased recreational screen time was "significantly associated" with higher cardiovascular risks and cardiometabolic risks among children and teens.

Study lead author Dr. David Horner, of the University of Copenhagen in Denmark, said: “Limiting discretionary screen time in childhood and adolescence may protect long-term heart and metabolic health.

“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, the research team 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.

The team developed a composite score based on a range 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 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," explained Dr. Horner.

“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.

“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 research team 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 a "significantly" higher risk associated with the same amount of screen time.

Dr. Horner said: “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.

“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.”

A machine learning analysis also identified a "unique" metabolic signature in the blood that appeared to be associated with screen time.

Dr. Horner said: “We were able to detect a set of blood-metabolite changes - a ‘screen-time fingerprint ’ - validating the potential biological impact of the screen time behaviour.

“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.

“Recognising and discussing screen habits during paediatric appointments could become part of broader lifestyle counselling, much like diet or physical activity.

“These results also open the door to using metabolomic signatures as early objective markers of lifestyle risk.”

Dr. Amanda Perak, chair of the American Heart Association’s Young Hearts Cardiovascular Disease Prevention Committee, said focusing on sleep is a great starting point to change screen time patterns.

Dr. Perak, of Northwestern University Feinberg School of Medicine in Chicago, said: “If cutting back on screen time feels difficult, start by moving screentime earlier and focusing on getting into bed earlier and for longer."

She said that adults can also set an example, adding: “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.”

Dr. Horner said 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.