New Data on how Second-Hand Smoke at Home Increases Risk for Children

Exposure to second hand smoke increases a child's risk of developing allergic rhinitis, allergic sensitivities, respiratory infections, and wheezing. Second-hand smoking also negates the positive effects of early exposure to household pets and the benefits of school asthma treatment programs. New data presented at annual meeting of the American Academy of Allergy, Asthma & Immunology (AAAAI) in San Francisco also show that parents who smoke are unlikely to stop smoking because a child has asthma.

"Tobacco smoke is a serious health risk," said Kathleen Sheerin, MD, of the Atlanta Allergy and Asthma Clinic. "It is especially dangerous for children because they have developing immune systems and developing respiratory systems, which puts them at increased risk for wheezing, coughing, and more frequent, more severe asthma attacks.

A genetic predisposition to allergies puts children at higher risk for developing allergies and wheezing if one or both of their parents smoke during pregnancy or the first decade of the child's life. Data presented at the AAAAI meeting, a study of 1,314 newborns in Germany, showed that environmental tobacco smoke increased the risk of allergic sensitization by 1.8 times if one parent had allergies. If both parents had allergies, the risk of allergic sensitization jumped seven-fold.

The study found similar results for wheezing, said Michael Kulig, PhD, associate professor at the Institute of Social Medicine in Berlin, Germany. In households where one or both parents smoked, having one atopic parent doubled the risk of wheezing during the first ten years of life. If both parents were atopic, the risk of wheezing increased 5.7 times.

There was no change in the risk of developing either allergic sensitization or wheezing in smoking households if neither parent had allergies.

"Genetic predisposition is the most important single factor for allergies," Dr Kulig said. "The child's risk is significantly higher if even one parent smokes." Overall, he said, about 40% of children in the study had no exposure to second-hand tobacco smoke at home, about 35% had irregular exposure, and about 25% had regular second hand smoke exposure.

In other research presented at the AAAAI meeting, child-protective measures such as inhaled corticosteroid therapy (ICS) at school or family pets early in life lose their value if parents smoke at home.

"Analysis told us that all of the significant improvements were produced by children who were not exposed to second-hand smoke at home," explained Robert Holzhauer, MD, clinical assistant professor of pediatrics at the University of Rochester School of Medicine. "When parents smoked at home, all the of benefits of inhaled corticosteroids disappeared. This shows the need for stronger persuasion to reduce sidestream smoke exposure."

Parental smoking also destroys the protective benefits of having dogs or cats at home during the early years of life. Dennis Ownby, MD, professor of pediatric and Internal Medicine at the Medical College of Georgia in Augusta, reanalyzed data from a landmark 2002 study showing that children who grow up with dogs or cats in the household have reduced rates of common allergies. The new analysis shows that the protective benefit of pets disappears when one or both parents smoke.

"Exposure to two or more dogs or cats in the first year of life reduces the risk of allergies by more than 50%," Dr. Ownby said. "Exposure to tobacco smoke negates the allergy protection that living with pets affords." Dr. Ownby was the lead researcher in both the original study and the reanalysis.

Researchers followed 474 healthy babies from birth until age 6 or 7. Sixteen percent of mothers and 24% of fathers reported that they smoked at home during the study period.

Children of nonsmoking parents were significantly less likely to be atopic if they were exposed to two or more cats or dogs than children exposed to one or no pets (14%, 28.8%, and 36.8% respectively, (P=0.0006). But exposure to two or more cats or dogs did not significantly change the risk of atopy in children of smoking parents (18.5%, 28.5%, and 24.6% respectively, (P=0.588). 

"Bottom line, cigarette smoke has a significant effect on the developing immune system of children," Dr. Ownby said. "Second-hand smoke is not as innocuous as parents might want to believe."

Another study, by Joel Liem, MD, of the University of Manitoba, Winnipeg, found that parents do not change their smoking behavior because one of their children has asthma. 

Dr. Liem surveyed more than 12,000 Manitoba households with children born in 1995. He got a 28% response rate from about 3,000 households. The overall smoking rate in the province fell from 32% to 23% during the seven-year period, but there was no association between smoking cessation and the asthma status of children in the household. 

"We found that childhood asthma does not play a role in parental decisions to quit smoking," Dr. Liem said. "Parents in Manitoba were quitting during the course of the study, but for other reasons. We were disappointed to see that smoking rates did not drop any faster in asthma homes than in homes where none of the children had asthma."

Source: PACT News