(March 5, 2009 - Insidermedicine) Preschoolers who are glued to the TV for two hours or more each day are nearly twice as likely to develop asthma as those who spend less time watching TV, according to research published in the journal Thorax.

Here are some warning signs that asthma might be developing in a child:

•    Coughing, especially at night and when the child has no cold

•    Wheezing, even if it is very light

•    Irregular breathing

Researchers from the University of Glasgow had parents estimate how many hours a day their 3.5 year old children spent watching TV. They then followed these children until they were 11.5 years of age. None of the children had signs of asthma at age 3.5.

Overall, 6% of the more than 3,000 children followed developed asthma. Those who watched TV more than 2 hours a day were nearly twice as likely to develop asthma as those who watched it only 1 to 2 hours a day.

We had a chance to speak with Dr. James Paton, one of the authors of this study, who offered some further insight.

Today’s research suggests that a sedentary lifestyle early in life may predispose children to develop asthma later on.

For Insidermedicine in Depth, I'm Dr. Susan Sharma.