Childhood Sedentary Time Linked To Young Adulthood Heart Damage

"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, Kuopio, Finland. "Children and teenagers need to move more to protect their long-term health."

Using smartwatches to assess movement, this study investigated the cumulative effects of sedentary time on young people and cardiac damage later in life, as part of the Children of the 90s Study that began in 1990 and is one one the world’s largest cohorts with lifestyle measurements from birth. 

766 children wore a smartwatch with an activity tracker for seven days at the ages of 11, 15, and 24 years old. The weight of the heart's left ventricle was assessed using echocardiography at 17 and 24 years of age. Associations between sedentary time between 11 and 24 years of age and heart measurements between 17 and 24 years of age were analyzed after adjusting for factors that could influence the relationships. 

The analysis revealed that at 11 years of age, the children were sedentary for an average of 362 minutes a day, increasing to 474 minutes in adolescence (15), and 531 minutes a day in young adulthood (24); representing an increase in sedentary time by an average of 169 minutes/2.8 hours a day between childhood and young adulthood. Additionally, every one-minute increase in sedentary time from the ages of 11 to 24 years old was associated with a 0.004 g/m increase in left ventricle mass between the ages of 17 to 24 years old. 

When multiplied by 169 minutes of additional inactivity this equates to a 0.7 g/m daily increase. This is the equivalent of a 3-gram increase; previous research has found that a similar increase in left ventricle mass over a 7-year period was associated with a twofold increase in the risk of heart disease, stroke, and death. 

Dr. Agbaje said: "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. As Martin Luther King Jr. once said, 'If you can't fly, run. If you can't run, walk. If you can't walk, crawl. But by all means keep moving.”