December 7, 2006 - Children and teenagers who smoke are up to four times more likely to develop asthma than nonsmokers, and the risk more than doubles if the child’s mother smoked while pregnant, a new study in the American Journal of Respiratory and Critical Care Medicine reveals.

Researchers have known that in utero exposure to the byproducts of cigarette smoke increases the risk of developing asthma during childhood, as does childhood exposure to second-hand smoke, but there was little data about the effect of a child or teen’s own smoking on asthma development or the combination of these factors. This new study followed the smoking habits of more than 2,500 fourth- and seventh-graders as they progressed to their senior year of high school. Those who reported smoking seven cigarettes a day on average and 300 cigarettes or more in the past year were 3.9 times more likely to develop asthma than nonsmokers. Children who smoked at these rates and whose mother smoked while pregnant were 8.8 times more likely to develop asthma.

The Institute of Medicine report Clearing the Air: Asthma and Indoor Air Exposures examines a variety of common indoor contaminants and found sufficient evidence of an association between environmental tobacco smoke and the development of asthma in younger children. The report also discusses evidence that implicates maternal smoking during pregnancy and calls for studies aimed at understanding the influence of genetic factors in this relationship. Clearing the Air also calls for further research exploring why children—especially young girls—start smoking and why pregnant women and mothers continue to smoke.

• Clearing the Air: Asthma and Indoor Air Exposures (2000)

• CDC