Dr. David Hill, a pediatrician who led a group that wrote the A.A.P.’s 2016 guidelines, said there are no known benefits of screen media for children under 18 months of age. But he added that technology is developing faster than the scientific study on the effect new devices are having on young brains.
Dr. Hill said the W.H.O. appears to be “applying the precautionary principle, and saying: ‘If we don’t know that it’s good, and there’s any reason to believe it’s bad, why do it?’”
The A.A.P. is beginning to contemplate the next set of guidelines, Dr. Hill said.
“It’s certainly possible as we revise our recommendations and as further data becomes available, we may skew that direction in the future,” he said. “But it’s hard to say without a comprehensive literature review, which is what informs our policy.”
The World Health Organization’s guidelines go further than the A.A.P’s recommendations.
Dr. Fiona Bull, a program manager for surveillance and population-based prevention of noncommunicable diseases at the W.H.O., led a team of experts who developed the guidelines.
“Improving physical activity, reducing sedentary time and ensuring quality sleep in young children will improve their physical, mental health and well-being and help prevent childhood obesity and associated diseases later in life,” Dr. Bull said in a statement.
The researchers also recommended that children under 5 not be restrained in strollers or high chairs or strapped to a caregiver’s back for more than one hour at a time. And children between the ages of 1 and 5 should get three hours of physical activity per day, and get at least 10 hours of sleep per night.
According to the W.H.O., the number of obese people worldwide has nearly tripled since 1974. Instances of childhood obesity, once considered a scourge of wealthy nations, are increasing dramatically in low- and middle-income countries, especially those in Africa and Asia.