乌鸦传媒

Limiting recreational screen time to less than 2 hours a day was linked to better neurocognitive development, a cross-sectional study of U.S. children found.

Superior global cognition was associated with limited screen time, adequate sleep, and adequate exercise in children, ages 9 and 10 years, with screen time and sleep having the strongest ties, reported Jeremy Walsh, PhD, formerly of the CHEO Research Institute in Ottawa and currently at the University of British Columbia, and colleagues in

"We don't know whether the association is due to the absence of more cognitively stimulating activities like reading or exposure to novel situations, or whether it's due to screen activity specifically," Walsh told 乌鸦传媒. "The literature is equivocal. Some findings show that people who are avid gamers have better visuospatial abilities and faster processing speeds and reaction times. But others show impairment in different types of attention and working memory."

Walsh's group analyzed data from 4,520 children in the Adolescent Brain Cognitive Development () project, a 10-year longitudinal, observational study across 21 sites in the U.S. They assessed children's behavior against the , which recommend 9 to 11 hours of sleep, <2 hours of recreational screen time, and at least 60 minutes of physical activity every day for children, ages 5-13 years.

The Canadian recommendations for physical activity and sleep are consistent with ones from the World Health Organization (WHO) and National Sleep Foundation, but neither organization, nor the American Academy of Pediatrics (AAP), has a recommendation about screen time for children, ages ≥5 years.

To measure global cognition, the researchers used the which spans six cognitive domains: language abilities, episodic memory, executive function, attention, working memory, and processing speed.

On average, children spent 3.6 hours engaged in recreational screen time each day. They met an average of 1.1 recommendations: 51% met the sleep recommendation, 37% screen time, and 18% physical activity. Almost 30% did not meet any recommendations and only 5% met all three.

Global cognition was associated positively with each additional recommendation met (Beta 1.44). Compared with meeting no recommendations, meeting all three recommendations was associated with superior global cognition (Beta 3.89); so was meeting only the recreational screen time recommendation (Beta 4.25), and meeting both the screen time and sleep recommendations (Beta 5.15).

While the link between cognition and physical activity was not as strong, this may be due to how exercise was measured in the ABCD study, Walsh said: the questionnaire asked how frequently children were active for ≥60 minutes, but did not ask about intensity, type, or duration.

The link between cognition and screen time potentially reflects an interruption of the stress-recovery cycle that children need for growth, observed Eduardo Esteban Bustamante, PhD, of the University of Illinois at Chicago, in an .

"Each minute spent on screens necessarily displaces a minute from sleep or cognitively challenging activities," he noted. When screens are used at night, this displacement may impair sleep.

"It is tempting to take solace in findings that cognitively challenging screen activities can benefit cognition, but, if given a choice, most children already consistently and predictably choose more stimulating screen activities over less stimulating ones," he added.

The study had limitations: It relied on self-reported answers to questionnaires that were administered only once, and residual confounding by unmeasured variables was possible.

The families create a personalized and designate media-free times throughout the day. Besides 1 hour of daily physical activity and 8-12 hours of sleep, the AAP recommends that children not sleep with digital devices -- including televisions, computers, and smartphones -- in their bedrooms, and that they avoid exposure to screens for 1 hour before bedtime.