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Secondhand Smoke Linked to Early Asthma

Living In Smoking Family Doubles Risk for Asthma by Age 6

WebMD Health News
Reviewed by Gary D. Vogin, MD

July 30, 2002 -- Families that smoke may be encouraging their habit -- as well as the health risks associated with it -- in their children. A new study shows children who grow up with smokers in the family not only face a bigger risk of developing asthma by age 6, but they are also more likely to become smokers themselves before their 15th birthday.

Researchers say that early exposure to smoke can speed the decline in lung function normally associated with age, increasing the risk of heart and lung problems or even death.

The study found the number of children who were diagnosed with asthma at age 6 or younger was twice as high if a family member smoked compared with those raised in nonsmoking families (6% vs. 3%).

In addition, children in families that had one or more smokers were more likely to start smoking earlier in life and become heavy smokers. The percentage of children who began smoking at age 15 or earlier was only 5% among nonsmoking families, but rose to 8% with one smoker in the family, 12% with three smokers, and 15% with four or more smokers.

For the study, researchers measured lung function in a diverse group of 4,000 black and white men and women who were between the ages of 18 and 30 when the study began in 1985-86. The participants had follow-up examinations two, five, and 10 years later and were asked questions about their respiratory health, cigarette use, and medical history.

About half of those surveyed said their mother smoked, and two-thirds said their father smoked. Only about 15% came from families with no smokers.

Nearly 44% of the participants had ever smoked, and about 20% were current smokers. The study found current smokers had a lower lung function at age 18 and had a faster rate of deterioration than nonsmokers. Researchers say the earlier the men or women started to smoke, the worse their lung function was likely to be.

The study also showed that the decline in lung function began earlier and was more rapid in smokers and in those who had asthma. And the combined effect of smoking and asthma on lung function decline was greater together than alone.

Although the study was unable to show a direct link between family smoking and problems with lung function, "family smoking did appear to influence the child's future behaviors that related to poorer [lung function]," writes study author David R. Jacobs Jr., PhD, of the School of Public Health at the University of Minnesota, Minneapolis, and colleagues.

Their complete report appears in the July 15 issue of the American Journal of Respiratory and Critical Care Medicine.

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