Think you know how much TV your kid is watching? If you’re not taking the time they spend in child care into account, you may be way off, according to a study from the University of Washington in Seattle.

That’s because on average children at center-based programs watch an average of about 0.4 hours of television a day, while those in home-based programs watch 2.4 hours a day, Dimitri A. Christakis and Michelle M. Garrison found in a phone survey of 168 child care programs in Michigan, Washington, Florida, and Massachusetts.

“For some children, this doubles their screen time,” Christakis told Reuters in a telephone interview.

Previous studies based on parents’ reports of their children’s TV watching have estimated that at home, children watch up to 2 and a half hours of television a day. That means some children are watching 5 hours of television a day, according to Christakis - nearly half of their waking hours.

Of the amount of time children in day care spend in front of the television, Christakis said, “I don’t think most parents are aware.”

Regardless of what kids are watching, watching television can slow language development, shorten attention span, decrease cognitive development, and contribute to obesity, the authors note.

Christakis also pointed to the “displacement phenomenon”; that is, “what would (kids) be doing if they were not watching TV?” Good daycare programs can provide an opportunity for kids to develop socially, mentally, and emotionally, said Christakis, noting that television does not add much of value.

Televisions, however, are common in the childcare setting: 70 percent of home-based programs in the study used televisions with preschoolers, and 36 percent of center-based programs did the same.

Christakis told Reuters Health that in 1970, on average, children began watching TV at 4 years of age, and watched less than 1 hour a day. Today, children begin watching at 4 months of age, and may be watching up to 4 to 5 hours a day.

The American Academy of Pediatrics recommends that children over 2 years of age watch no more than 2 hours of television daily. Christakis suggested that parents ask their day care centers about the time their children spend in front of the television, and, if necessary, request alternative activities.

SOURCE: Pediatrics, December 2009.