The finding is based on the tracking of COPD risk among nearly 1,400 adults, and it suggests that heavy maternal smoking -- more than 20 cigarettes per day -- increases a child's long-term COPD risk nearly threefold.
"The findings were not surprising to us," said study author Jennifer Perret. She is a postdoctoral fellow with the Centre for Air Quality and Evaluation in the Melbourne School of Population & Global Health at the University of Melbourne in Australia.
"Smoking in later life can result in deficits in lung function by middle age. So it was not unexpected to see that mothers' smoking . . . could also adversely influence the growing lungs of [their children]," Perret said. And, "reduced lung function potential in childhood predisposes an individual to having reduced lung function as an adult," she added.
However, the study did not prove that a mother's heavy smoking habit caused her children to have an increased risk for COPD later in life; the researchers only found an association.
Perret and her colleagues reported their findings in the Thursday issue of the journal Respirology.
According to the U.S. National Heart, Lung, and Blood Institute, COPD is a progressively worsening illness that greatly compromises a person's ability to breathe. Smoking is the leading cause of COPD, which is now the third leading cause of death around the world, the researchers said.
To see how COPD risk related to parental smoking patterns, the authors reviewed surveys completed in 2004 by more than 5,700 men and women (average age of 45) who had been participating in a long-running study that began in 1968.
Nearly 40 percent said that when they were 7 years old, they lived with a mother who smoked, and 17 percent of this group said their mothers were heavy smokers. Nearly 60 percent grew up with smoking fathers, 34 percent of whom were heavy smokers.
Twelve percent said they grew up in households where both parents were heavy smokers. Only 8 percent grew up in a household where the mom was the sole smoker.
About two-thirds of the study participants said they had a history of asthma, and one-quarter said they still had the respiratory condition. More than 4 in 10 said they had never smoked themselves.
Nearly 1,400 of the survey respondents underwent lung-function tests between 2006 and 2008. The investigators uncovered no evidence of elevated COPD risk among those who had grown up with smoking dads, or moms who smoked less than 20 cigarettes a day.
But those who grew up with mothers who smoked heavily were 2.7 times more likely than others to have a kind of lung impairment that is indicative of COPD. Additional testing revealed that the already elevated risk for COPD seen among offspring who smoked themselves was driven even higher if they had grown up with a mom who smoked heavily.
There were indications that boys might be somewhat more vulnerable to the negative impact of maternal smoking than girls. Perret suggested this could be due to a range of gender-based "biological differences" that unfold throughout childhood development.
Regardless, the team said the findings should bolster current recommendations that pregnant women and young mothers should avoid smoking altogether.
Meanwhile, for those whose moms smoked heavily, what can be done to minimize their COPD risk?
"If there are concerns or symptoms such as breathlessness on exertion, cough or phlegm, they may wish to seek the advice of a doctor who could measure their lung function," Perret advised. And, she suggested, "as there may be a combined effect with other smoking and environmental exposures, it would be advisable for them not to smoke, and avoid smoky, dusty and polluted environments where possible."
Dr. David Mannino, chief scientific officer for the COPD Foundation, expressed little surprise at the findings.
But he cautioned that there is no specific magic bullet for reducing COPD risk among those with this kind of family history.
As for everyone, said Mannino, the focus should be placed on the "same factors that are important to maintaining good health: Don't smoke, exercise and watch your diet."More information
There's more on COPD at the U.S. National Heart, Lung, and Blood Institute.
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