Researchers in the UK report finding that young children who watch more than two hours of television a day nearly double their risk of developing asthma by the time they are teenagers. According to scientists, time spent watching TV may be a proxy measure of a sedentary lifestyle, which may be the root cause of the increase in asthma risk.

The study, published in the journal Thorax, tracked the health of over 3,000 children in the UK from birth to age 11½. As part of the study, parents were asked to report on the time their kids spent watching TV starting from age 3½. The parents were also asked about symptoms of wheezing among their children and whether their child had been diagnosed with asthma. None of the children involved in the study had symptoms of asthma as infants and toddlers.

By the time the children had reached almost twelve years of age, 6% had developed asthma. The children whose parents reported that they watched TV for more than two hours a day were nearly twice as likely to have been diagnosed with asthma as those who watched less TV.

Among the children diagnosed with asthma, 2% did not watch TV, 20% watched TV for less than one hour a day, 24% watched 1-2 hours of TV a day, and 44 % watched more than two hours of TV daily.

The researchers believe that inactivity is the cause of the increase in asthma risk instead of TV watching per se. Kids who watch more TV tend to have a more sedentary lifestyle and get less overall physical activity. Other studies have found a relationship between asthma risk, lack of activity, and being overweight. It may be that physical activity, which requires deeper breathing, somehow stretches and conditions the lungs, protecting the airways. Scientists have found some evidence that breathing patterns may affect the responsiveness of smooth muscles in the lung airways, muscles that become hyper-responsive in those with asthma. Perhaps failure to stretch these muscles in childhood can increase the likelihood that these muscles will become hyper-responsive.

The study authors note that it is unlikely that the children who developed asthma simply watched more TV because they had breathing problems and could not perform physical activity, because none of the children involved in the study had any asthma symptoms at the study’s outset. Also, there was little difference in the exercise levels of those with asthma and those without at age 11½.

For more information on asthma prevention, read "How Can I Prevent Asthma?" in the Healia Health Guide to asthma. Share your own experiences with asthma at the Healia Health Community for Asthma.

_{Photo: Axel Buhrmann, Flickr, Creative Commons}