Chicago ? Very young children who watch television face an increased risk of attention deficit problems by school age, a study has found, suggesting that television might overstimulate and permanently “rewire” the developing brain.

For every hour of television watched daily, two groups of children, aged 1 and 3, faced a 10 percent increased risk of having attention problems at age 7.

The findings bolster previous research showing that television can shorten attention spans and support American Academy of Pediatrics recommendations that youngsters under age 2 not watch television.

“The truth is there are lots of reasons for children not to watch television. Other studies have shown it to be associated with obesity and aggressiveness,” too, said lead author Dr. Dimitri Christakis, a researcher at Children’s Hospital and Regional Medical Center in Seattle.

The study, appearing in the April issue of Pediatrics, involved 1,345 children who participated in government-sponsored national health surveys. Their parents were questioned about the children’s TV viewing habits and rated their behavior at age 7 on a scale similar to measures used in diagnosing attention deficit disorders.

The researchers lacked data on whether the youngsters were diagnosed with attention deficit disorders, but the number of children whose parents rated them as having attention problems — 10 percent — is similar to the prevalence in the general population, Christakis said. Problems included difficulty concentrating, acting restless and impulsive, and being easily confused.

About 36 percent of the 1-year-olds watched no television, while 37 percent watched one to two hours daily and had a 10 percent to 20 percent increased risk of attention problems. Fourteen percent watched three to four hours daily and had a 30 percent to 40 percent increased risk compared with children who watched no TV. The remainder watched at least five hours daily.

Among 3-year-olds, only 7 percent watched no television, 44 percent watched one to two hours daily, 27 percent watched three to four hours daily, almost 11 percent watched five to six hours daily, and about 10 percent watched seven or more hours daily.

The researchers didn’t know what shows the children watched, but Christakis said content likely isn’t the culprit. Instead, he said, unrealistically fast-paced visual images typical of most TV programming may alter normal brain development.

“The newborn brain develops very rapidly during the first two to three years of life. It’s really being wired” during that time, Christakis said.

Overstimulation during this critical period “can create habits of the mind that are ultimately deleterious,” Christakis said.