More and more children are getting asthma. In fact, the number of children younger than age 5 with asthma has risen 160% in the last 15 years. The number of school-age children with the condition increased 75% in that time.

Experts are still trying to determine exactly what is behind these dramatic increases. They have determined that some children are more likely to get asthma than others. These include:

• children with a history of asthma in their families
• overweight children
• children with allergies.

Children who live in cities also have a higher risk of asthma. Poor housing, bad diet, and other factors may be to blame. One study showed that the reason African-American children develop asthma more frequently than Caucasian children is simply because they're more likely to live in cities.

Boys are more likely to develop asthma before puberty than girls. But girls have a higher risk of the condition after puberty. One reason may be that, during infancy, boys tend to have smaller airways than girls. Then, after puberty, boys have larger airways than girls.