(Health.com) -- Young children in the United States watch about 80 minutes of television per day, on average.
Depending on whether the programming is educational and age-appropriate, all that time in front of the tube can either help or harm their development, research suggests.
But what happens in that 80 minutes may be only part of the story. According to a nationwide study, a much bigger proportion of kids' TV exposure comes indirectly, from television that's on in the background while they're doing other activities.
The average child between the ages of 8 months and 8 years absorbs nearly four hours of this so-called background or "secondhand" TV each day, the study found. And this indirect exposure, by detracting from play, homework, and family time, may have possible consequences for kids' well-being.
This is the first study to quantify background television in children, and the high number is "surprising," says lead author Matthew Lapierre, an assistant professor of communication studies at the University of North Carolina Wilmington.
"From a research perspective, I would be very concerned," Lapierre says. "I think (background TV) is something that researchers need to spend more attention to, to understand and unpack."
Lapierre and his colleagues arrived at their estimates by interviewing a nationally representative sample of parents about their household's TV habits on a typical weekday and weekend.
Background TV was especially common in certain populations. Children under the age of 2, African-American children, children living in poverty and kids with less-educated parents had the highest levels of exposure -- at least five hours per day. Conversely, exposure ranged from 2.5 to three hours per day among whites and children from more affluent families.
The study appears in the November issue of the journal Pediatrics. Lapierre presented preliminary findings from the study last spring at the annual meeting of the International Communication Association, a group of communications scholars.
No one really knows what kind of impact background TV has on a child's development, Lapierre says. A handful of small studies have linked background TV to shorter attention spans, lower quality parent-child interactions, and poorer academic performance, but the research on this topic is still in the early stages.
The impact likely depends on a child's age, and what he or she happens to be doing while the TV is on, says Sara Rivero-Conil, a pediatric psychologist at Miami Children's Hospital.
A toddler, for instance, "is developing and learning how to play," Rivero-Conil says. "Background television is decreasing their attention to the play at hand. You're taxing something that's already limited."
The constant flickering and sound of a nearby TV may be even more distracting to school-age children, Rivero-Conil adds. As kids get older, they're more likely to be drawn to the actual content on the screen, at the expense of their homework or other tasks.
Despite the limited research, background TV has gotten the attention of pediatricians. A 2011 policy statement from the American Academy of Pediatrics (which publishes Pediatrics) included a section on secondhand TV, and urged parents with children under age two to be mindful that their own TV watching "can have a negative effect on their children" and "is distracting for both the parents and the child."
The good news is that limiting background TV is easy. Parents can simply turn the television off when no one's watching, and make sure it stays off during homework time, meal times and bedtime.
"These are good points in the day to limit TV. It should be standard practice for kids growing up to know this," Rivero-Conil says. "It also forces families to talk about each other's day."
But perhaps the single most important step parents can take is to "get the TV out of the bedroom," Lapierre says. "There's overwhelming evidence that having a television in a child's bedroom is really not a good thing."
Children who have a TV in their room have a higher risk of obesity, poor sleep habits and lower academic achievement. And in the new study, not surprisingly, kids who slept in the same room as a TV received an extra hour of background exposure per day.
"That's substantial," Lapierre says.
Copyright Health Magazine 2011