Secondhand tobacco exposure early in life may decrease lung function in childhood
Secondhand exposure to tobacco smoke in utero and in early childhood was associated with decreased lung function by age 6, according to research presented at the American Thoracic Society International Conference.
“Previous studies have established an association between tobacco smoke exposure and decreased target lung function,” Hanna Knihtilä, MD, PhD, research fellow in the Channing Division of Network Medicine, Brigham and Women’s Hospital and Harvard Medical School, said during a presentation. “However, most of these studies only measure the exposure at one time point and were based on Western data, which tend to underestimate ... secondhand exposure.”
The study evaluated 476 mother-child pairs from the Vitamin D Antenatal Asthma Reduction Trial, which enrolled pregnant women at 10 to 18 gestational weeks who reported no smoking. Researchers administered questionnaires to collect information on active smoking and household smoking exposure during pregnancy and at 1, 3 and 6 years after delivery. Researchers also measured plasma cotinine levels at 10 to 18 weeks’ gestation and 32 to 38 weeks’ gestation and age 1, 3 and 6 years to assess cumulative tobacco smoke exposure at each time point.
At age 6 years, each child’s lung function was measured using spirometry and impulse oscillometry.
Sixty-five (14%) mothers reported active smoking and 103 (22%) reported other household smoking during at least one time point.
Active maternal smoking (P < .001) and household smoking (P < .05) were associated with an increase in cotinine levels in mothers during pregnancy and in their respective children at age 1 and 3 years. However, household smoking at 10 to 18 gestational weeks was not associated with maternal cotinine level (P = .074).
There was no association between household smoking (P = .29) or maternal active smoking (P = .82) and increased cotinine levels among children at age 6 years.
Reflected by increased blood cotinine levels during pregnancy and early life, cumulative tobacco smoke exposure during gestation and childhood years was associated with decreased lung function in children at age 6 years. The strongest effects of decreased lung function at age 6 years were observed among the cumulation of smoke exposure from pregnancy to childhood together.
In addition, researchers reported no association between cotinine level and children’s lung function among offspring of mothers with sufficient vitamin D levels throughout pregnancy, but reported significant effects among those with insufficient vitamin D levels during pregnancy.
Results from this study may serve as objective data for health care providers and families to advocate tobacco smoke exposure minimalization from pregnancy to childhood, according to a related press release.
“Household smoking results in increased plasma cotinine levels in pregnant women and children, but high cotinine levels can also be seen in subjects without reported exposure,” Knihtilä said. “Furthermore, even small amounts of secondhand tobacco smoke exposure from pregnancy to childhood can lead to dose- and duration-dependent decrease in child lung function at age 6. However, gestational vitamin D might provide protection against this effect.”