Not moving enough can have life-threatening ­consequences – and it is an equally serious problem for children as it is for adults.

An inactive childhood could ­increase the chance of heart attacks and strokes later in life, a study has revealed, and our kids and teenagers must get off their screens more to ­protect their long-term health.

Researchers from the universities of Exeter, Bristol and Eastern Finland found sedentary time ­accumulated in childhood and young adulthood is linked to heart damage and the effect of inactivity is long term.

Lead author Dr Andrew Agbaje, of Exeter University, has a stark warning.

“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,” he said.

“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 to move more by taking them out for a walk and limiting screen time.”

This research is the first to look into the cumulative effect of sedentary time in young people and subsequent cardiac damage in later life.

At 11 years of age, children in the study wore a smartwatch with an activity tracker for seven days.

This was repeated at 15 years of age and again at 24. In parallel, the weight of the heart’s left ventricle, its main pumping organ, was measured by an echo-cardiography – a type of ultrasound scan – at 17 and 24.

The researchers analysed the association between sedentary time at 11 and 24 and heart measurements at 17 and 24. The study included 766 ­children of whom 55% were girls and 45% were boys.

At 11, children were sedentary for an average of 362 minutes a day, rising to 474 minutes at 15 years of age, and 531 minutes at 24 years of age.

This means that sedentary time increased by an average of 169 minutes (2.8 hours) a day between childhood and young adulthood.

A previous study in adults found a similar increase in left ventricular weight over a seven-year period led to a two-fold increased risk of heart disease, stroke, and death.

Each one-minute increase in ­sedentary time from 11 to 24 years results in an increase in left ventricular mass between 17 to 24 years of age.

And 169 minutes of inactivity equates to a 3g increase in left ­ventricular mass. Frightening.