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July 1, 2005 -- Adults may be more likely to have asthma if they were exposed to tobacco smoke before birth or in childhood.
The finding appears in the American Journal of Respiratory and Critical Care Medicine.
Researchers working on the study included Trude Duelien Skorge, MD, of the thoracic medicine department of Haukeland University Hospital in Bergen, Norway.
Researchers' Comments
The findings don't prove a direct connection; instead, they indicate a possible link.
Direct evidence that active smoking causes asthma is "scant," say the researchers.
However, they say several interesting findings show that exposure to maternal smoking before birth and during development and/or environmental tobacco smoke in childhood may play a part.
Passive smoking exposure, both before and after birth, has been linked with respiratory symptoms and asthma in childhood, say the researchers.
Adults who have never smoked and are exposed to tobacco smoke at home or work have also been linked to a higher risk of respiratory symptoms and asthma, they say.
Long-Term Study
The study, done in western Norway, lasted 11 years. More than 2,800 people were included. They were 15 to 70 years old.
Participants were asked if they'd ever been treated or hospitalized for asthma. They were also asked about their prenatal or childhood exposure to smoke.
"About one in 10 said their mothers had smoked while pregnant with them," say the researchers. "A little less than a quarter reported that their mothers had smoked while they were children."
About 60% said they had been exposed to secondhand smoke from someone else in the house, say Skorge and colleagues.
Risk Highest With Prenatal Smoke Exposure
Those with prenatal exposure to smoke had a higher risk for adult asthma. The trend was weaker for maternal smoking in childhood, say the researchers.
The researchers say they did "extensive adjustments" to take other risk factors into account. It's possible that some people didn't correctly report their smoke exposure.
Still, they say nearly a quarter of new cases of adult asthma were attributable to pre- or postnatal smoking.
More studies are needed to verify the finding and probe the topic further, say the researchers.
CDC's List of Asthma Triggers
About 20 million Americans had asthma in 2001, says the CDC. Asthma is the most common long-term disease in children.
People may be more vulnerable to asthma if it runs in their families, but in most cases, the precise cause isn't known, says the CDC.
The CDC's list of possible asthma triggers includes:
Strenuous exercise, bad weather conditions, and some foods and drugs may also be asthma triggers, says the CDC. Strong emotional states can also lead to hyperventilation and an asthma episode, says the CDC.
People with asthma should learn and avoid their triggers, says the CDC.
Medical experts also discourage smoking for many health reasons, whether children are present or not.
SOURCES: Skorge, T. American Journal of Respiratory and Critical Care Medicine, July 1, 2005; vol 172: pp 61-66. CDC: "Basic Facts About Asthma." News release, American Thoracic Society.