On average, children aged eight to 11 spent 3.6 hours per day glued to a TV, mobile phone, tablet or computer screen, almost double the suggested limit of two hours, researchers found.
A new study published by Lancet Child and Adolescent Health, examined 4,500 United States children aged between eight and 11 to determine how screen time affects their cognitive development.
Half of the children met the sleep recommendation (51%, 2,303/4,520), 37% (1,655/4,520 children) met the screen time recommendation, and 18% (793/4,520 children) met the physical activity recommendation. The more recommendations the child met, the better their cognitive development, according to the study.
"These findings highlight the importance of limiting recreational screen time and encouraging healthy sleep to improve cognition in children, " the study's authors wrote. The results were adjusted after considering factors like household income, puberty development, and others - all of which could affect performance.
"We really had an opportunity here to look at how meeting each of these guidelines and meeting all of the guidelines relate to cognition in a large sample of American children". "In the case of evening screen use, this displacement may also be compounded by impairment of sleep quality", he said.
Provided they have sufficient sleep and physical activity. She was not involved in the study.
However, only one in 20 USA children in the study met the three recommendations advised by the Canadian 24-hour Movement Guidelines to ensure good cognitive development.
"Each minute spent on screens necessarily displaces a minute from sleep or cognitively challenging activities", Dr. Bustamante wrote in a commentary that accompanied the study. "If we are to do a better job of protecting children's minds than their bodies, we will need to be better scientists and citizens than we have been".
"I think that the overarching goal here is that parents should consider the whole 24-hour day of their children and put realistic rules or limits in place for how long they are on their screens for, having bedtime rules, and making sure to encourage physical activity", Walsh said. The study's authors said that more research is needed to probe the links between screen time and cognition, including research differentiates between different types of screen time activities and what effects they have on children.
Nicky Mehtani is an internal medicine physician at Johns Hopkins Hospital and a part of the ABC News Medical Unit.