A child’s cognition can be improved by getting nine to 11 hours sleep and limiting their screen time to less than two hours per day, a major study has found.
Limiting recreational screen time to less than two hours a day, and having sufficient sleep and physical activity is associated with improved cognition, compared with not meeting any recommendations, according to an observational study of more than 4,500 US children aged 8-11 years published in the Lancet Child & Adolescent Health journal.
Only one in 20 US children in the study met the full recommended guidelines on recreational screen time, physical activity and sleep.
Taken individually, limited screen time and improved sleep were associated with the strongest links to improved cognition, while physical activity may be more important for physical health.
The study found that US children spend an average of 3.6 hours a day engaged in recreational screen time.
The authors say their findings indicate that adhering to the guidelines during childhood and adolescence, particularly for screen time, is important for cognitive development.
“Behaviours and day-to-day activities contribute to brain and cognitive development in children, and physical activity, sedentary behaviour, and sleep might independently and collectively affect cognition,” says Dr Jeremy Walsh, CHEO Research Institute, Ottawa, Canada.
Academic performance
“Evidence suggests that good sleep and physical activity are associated with improved academic performance, while physical activity is also linked to better reaction time, attention, memory, and inhibition. The link between sedentary behaviours, like recreational screen time, is unclear, as this research is in the early stages and it appears to vary depending on the types of screen-based activity,” said Dr Walsh.
In the study, data from 4,520 children at 20 sites across the US was analysed. Children and parents completed questionnaires and measures at the outset of the trial to estimate the child’s physical activity, sleep and screen time. Children also completed a cognition test, which assessed language abilities, episodic memory, executive function, attention, working memory and processing speed.
The study controlled for household income, parental and child education, ethnicity, pubertal development, body mass index and whether the child had had a traumatic brain injury.
It found that meeting only the screen time recommendation or both the screen time and sleep recommendations had the strongest associations with cognitive development.
Although there is substantial evidence for the association between physical activity and cognitive development in the study, meeting the physical activity recommendation alone showed no association with cognition.
Surprising finding
The authors note this was a surprising finding and may suggest that the measure used may not have been specific enough.
They note that physical activity remains the most important behaviour for physical health outcomes, and there is no indication that it negatively affects cognition.
Dr Walsh said they found that more than two hours of recreational screen time in children was associated with poorer cognitive development.
“More research into the links between screen time and cognition is now needed, including studying the effect of different types of screen time, whether content is educational or entertainment, and whether it requires focus or involves multitasking. Based on our findings, paediatricians, parents, educators, and policymakers should promote limiting recreational screen time and prioritising healthy sleep routines throughout childhood and adolescence,” he said.