*The following is excerpted from an online article posted on HealthDay.
If you're worried that too much "screen time" could be sapping your child's intelligence, new research suggests you might be right.
Kids with the sharpest intellects spent less than two hours a day on their cellphones, tablets and computers, coupled with 9 to 11 hours of sleep and at least an hour of physical activity, the study found.
Unfortunately, very few U.S. children meet all three of these daily goals, said lead researcher Jeremy Walsh, a postdoctoral fellow with the CHEO Research Institute in Ottawa, Canada.
"Only 5 percent of our sample met all three guidelines," Walsh said.
About 41 percent met one of the guidelines and 25 percent met two, he continued.
"That means 30 percent of our sample didn't meet any of the guidelines, which I think is a very important statistic to focus on," Walsh said.
The study is based on data gathered from over 4,500 U.S. kids aged 8 to 11 between September 2016 and September 2017 as part of a new, federally funded 10-year study on brain development and child health.
Walsh and his colleagues used the data to see if children are limiting their screen time while also getting enough sleep and exercise, based on Canadian guidelines published in 2016.
Half of the children got the recommended 9 to 11 hours of sleep, 37 percent met the screen time guideline of less than two hours, and 18 percent got an hour or more of exercise. On average, the kids in the study spent 3.6 hours a day engaged in screen time.
The study couldn't prove cause-and-effect, but the more individual recommendations a child met, the better their ability to think and reason. That's what the researchers found when they compared guideline adherence against performance on brain exercises ("cognition").
Kids who met the sleep and screen time guidelines appeared to have the best intellects, followed by the kids who met just the screen time guidelines, the findings showed.
Too much screen time could be wrecking kids' ability to focus, especially if they are switching between apps on a device or between different screens at the same time, Walsh suggested.
The findings were published online Sept. 26 in The Lancet: Child & Adolescent Healthjournal.
According to Dr. Shawna Newman, an attending psychiatrist at Lenox Hill Hospital in New York City, the study "clearly demonstrates the specific benefit of exercise for children, in addition to that of good sleep hygiene and the limitation of screen time contributing positively to cognitive development." Newman was not involved with the new study.