Parents should limit the amount of time children spend on social media and video games, researchers have said, after a new study found inactive teenagers are more likely to have signs of heart damage when they are young adults.
Academics said that this heart damage could be setting the stage for heart attacks and strokes in later life.
Even children who have a normal weight were still at risk, experts found.
In the new study 766 British youngsters were tracked for 13 years.
Sitting time was assessed using smartwatches with an activity tracker for seven days.
Children aged 11 were assessed to see how much time they were inactive each day.
This assessment was repeated when they were 15 and again when they were 24.
Researchers also performed ultrasound scans on the hearts of older teenagers and young adults.
The scans were used to assess the weight of the heart’s left ventricle.
An increased left ventricle is a “strong predictor” for adverse heart events in adulthood and is used as a tool to assess “premature cardiac damage” in children and young adults, they said.
The researchers then looked a periods of inactivity to see whether more time spent sitting is linked to increased “left ventricular mass”.
The average time spent sitting increased from six hours among 11-year-olds to nine hours among 24-year-olds, according to the study, which is to be published at the ESC Congress in Amsterdam.
Parents should encourage children and teenagers to move more by taking them out for a walk and limiting time spent on social media and video games— Dr Andrew Agbaje
The researchers found that each one-minute increase in sedentary time from 11 to 24 years old was associated with a 0.004g/m2.7 (grams relative to height) increase in left ventricular mass between 17 and 24 years old.
“All those hours of screen time in young people add up to a heavier heart, which we know from studies in adults raises the likelihood of heart attack and stroke,” said study author Dr Andrew Agbaje of the University of Eastern Finland.
“Children and teenagers need to move more to protect their long-term health.”
“Children were sedentary for more than six hours a day and this increased by nearly three hours a day by the time they reached young adulthood.
“Our study indicates that the accumulation of inactive time is related to heart damage regardless of body weight and blood pressure.
“Parents should encourage children and teenagers to move more by taking them out for a walk and limiting time spent on social media and video games.”
It can be challenging to keep children moving, especially as they get older, but the importance of regular physical activity throughout life cannot be overstated, and the need to stay active starts early— Dr Sonya Babu Narayan, British Heart Foundation
Dr Sonya Babu Narayan, associate medical director at the British Heart Foundation, said: “This study highlights that even if we look healthy from the outside, inactivity may lead to silent changes accumulating in our heart that could increase our risk of cardiovascular disease in later life.
“More research will be needed to understand why increased sedentary time was linked to an even greater impact over time on young women’s hearts than seen for young men.
“It can be challenging to keep children moving, especially as they get older, but the importance of regular physical activity throughout life cannot be overstated, and the need to stay active starts early.
“The NHS advice is that children aged five to 18 should aim to get at least 60 minutes of moderate or vigorous intensity physical activity each day across the week.
“As we move into adulthood, we should be aiming for at least 150 minutes of moderate intensity physical activity each week.”
