Kids who smoked have higher asthma risk

NEW YORK, Nov28 (Reuters) Children who smoke are almost four times more likely to develop asthma than those who don't smoke, and their risk is even greater if their mothers smoked while pregnant with them, a new study shows.

The increased risk of developing an activity-limiting chronic disease, such as asthma, after becoming a regular smoker ''may provide new motivation for adolescents to refrain from smoking,'' Dr Frank D Gilliland of the University of Southern California in Los Angeles and colleagues state.

While a mother's exposure to second-hand smoke during pregnancy has been tied to greater childhood asthma risk, along with being exposed to second-hand smoke in childhood, the effect of a child or teen's own smoking on asthma development is less clear, Gilliland and his team write.

To investigate, they followed 2,609 fourth- and seventh-graders in 12 southern California communities through their graduation from high school. Researchers interviewed the study participants annually and classified them according to smoking status.

During follow-up, 28 per cent of the children reported any smoking at all, while 13.8 per cent smoked weekly and 6.9 per cent smoked daily (regular smokers).

Children who said they smoked seven cigarettes a week in the previous year had a 3.1-times greater risk of developing asthma during the course of the study, while those who had smoked at least 300 cigarettes in the past year were at 3.9-fold increased risk.

And children exposed to their mother's smoking while in the womb who later took up the habit themselves were 8.8-times more likely to develop asthma. When the researchers separated out children who smoked regularly but whose mothers had not smoked while pregnant with them, they found their risk of asthma was increased by just 20 percent.

Adolescents who had no allergies were at greater risk of developing asthma if they smoked than were non-allergic kids, the researchers found. Non-allergic kids who smoked and whose mothers had smoked during pregnancy were at a 10.6-fold increased asthma risk.

Gilliland and his team previously proposed that exposure to cigarette smoke in the womb might make adolescents more vulnerable to developing asthma if they started smoking themselves.

''Effective tobacco control efforts focusing on the prevention of smoking among children, adolescents, and women of childbearing age are urgently needed to reduce the number of these preventable cases of asthma,'' the researchers conclude.

REUTERS SP PM0953