That clamor in the background? It's probably the TV, and it might be taking a toll on your toddler's development, researchers say.

According to the first national estimate of background television exposure, children in the U.S. spend nearly as much time around a switched-on television as they do in school.

Between the age of eight months and eight years, kids spend an average of 232 minutes a day with the TV droning on in the background, researchers found. Add to that the 80 minutes of active watching that previous studies have found, and you land at just over five hours of daily interaction with the electronic babysitter.

"It's quite an alarming study," said Dr. Victor Strasburger, a pediatrician who has studied media use in youngsters, but was not involved in the new survey.

"This is a clear warning signal to parents that if they are not watching TV, they ought to turn it off, and a reminder that parents should be avoiding screen time in infants under two," added Strasburger, of the University of New Mexico in Albuquerque.

The results are based on nationally representative telephone interviews with close to 1,500 parents, who reported their child's activities over the past 24 hours and whether there was a TV on in the background.

The effects of screen time on developing brains and minds are not well understood, but researchers say concerning findings are emerging.

For instance, children spend less time playing with friends and interacting with parents when a TV is clamoring in the background than when there is no such distraction, said Matthew Lapierre of the University of North Carolina Wilmington, who led the new survey.

"We definitely need to rethink this sort of exposure," he told Reuters Health. "You have learned how to deal with this, but what does it mean for a very young child?"

Lapierre and his colleagues found that the younger children were, the more background TV they were exposed to. Toddlers under two, for example, spent 5.5 hours around the screen daily.

Kids with a TV in the bedroom and African Americans also had more exposure, according to the report, published Monday in the journal Pediatrics.

The American Academy of Pediatrics recommends limiting media time for kids to less than two hours per day, keeping the TV set and Internet out of the bedroom and avoiding screen time for kids under two.

Surfing the Web or watching TV before bedtime has been linked to sleep problems and drowsiness during the day in kids. Researchers also worry that screen time may lead youth to snack more and to pick up bad habits, such as smoking and drinking in excess.

For infants and toddlers, studies suggest the din from a TV may slow down language development, according to Strasburger.

"Think about it," he said. "It's confusing for babies who are trying to get their language together to have indistinguishable voices in the background."

Strasburger said young infants distinguish between people on TV and flesh-and-blood humans, and they learn better from the latter. When he walks into an examination room, the pediatrician added, he can tell which toddlers are watching TV and which ones have parents reading to them.

"The babies that are being read to are just chattering away, and the babies that sit in front of a TV are silent," he said. "It means their language development is threatened - they may catch up, but it's a concern."