London, Aug 23 : No activity for hours during childhood could be setting the stage for heart attacks and strokes later in life, a new study said on Wednesday.  According to the study presented at the European Society of Cardiology, sedentary time accumulated from childhood to young adulthood was associated with heart damage -- even in those with normal weight and blood pressure. "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 Andrew Agbaje of the University of Eastern Finland, Kuopio, Finland. "Children and teenagers need to move more to protect their long-term health," he added. To investigate, researchers let children wear a smartwatch with an activity tracker for seven days at 11 years of age. This was repeated at 15 years of age and again at 24 years of age. The weight of the heart's left ventricle was assessed by echocardiography, a type of ultrasound scan, at 17 and 24 years of age and reported in grams relative to height (g/m2.7). The researchers analysed the association between sedentary time between 11 and 24 years of age and heart measurements between 17 and 24 years of age after adjusting for factors that could influence the relationship, including age, sex, blood pressure, body fat, smoking, physical activity and socioeconomic status. The study included 766 children, of which 55 per cent were girls and 45 per cent were boys. At 11 years of age, children were sedentary for an average of 362 minutes a day, rising to 474 minutes a day in adolescence (15 years of age), and 531 minutes a day in young adulthood (24 years of age), meaning sedentary time raised by an average of 169 minutes (2.8 hours) a day between childhood and young adulthood, the study showed. "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," Agbaje said. /IANS