Asthma Risk From Smoking May Start Early
Possible Link May Begin Before Birth, Say Norwegian Researchers
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.
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.
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.