Girls are more affected by secondhand smoke than boys, a new study has found.
Research from the University of Cincinnati (UC) in the U.S. found that being exposed to smoke in early childhood appears to impact girls more than boys, especially if they already have allergies.
Epidemiologists with the university’s Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS), discovered that two-year-olds exposed to high levels of secondhand smoke, who also have other allergies, are at a greater risk of decreased lung function at the age seven compared to children who do not have any allergies.
Also, researchers say that lung function among girls was six times worse than in boys who are exposed to similar levels of both secondhand smoke and allergen sensitisation.
"Our study shows that the timing of allergic sensitisation is crucial because children who are sensitised by age two are more likely to suffer the greatest lung deficits during childhood as a result of secondhand smoke exposure,” explains Kelly Brunst, doctoral candidate in UC’s division of epidemiology and biostatistics. "This association was not observed at age four or seven, emphasising the importance of this critical window for lung development.”
The UC-based team’s findings are published online ahead of print in the scientific journal Pediatric Allergy and Immunology.
Researchers measured secondhand smoke levels by studying hair samples from the children to assess levels of cotinine (a product of nicotine metabolism).
Previous studies have estimated that one in four children in the U.S. living in a home with at least one smoker have cotinine concentrations more than twice as high as those living with non-smoking adults. Secondhand smoke exposure during childhood has also been associated with respiratory illness, decreased lung function and asthma.
"Our results provide valuable information regarding the interwoven relationships between early-life exposure to secondhand tobacco smoke, allergic sensitisation, gender and lung function,” says Grace LeMasters, principal investigator of the CCAAPS.
"It’s likely that the complex interaction between secondhand smoke and pulmonary function loss in boys and girls is ultimately dependent on the timing of exposure as well as the child’s ‘total load’ in relationship to cumulative risk factors—exposures, allergic sensitisation, asthma status, genetic susceptibility and sex hormones.”
CCAAPS is a long term childhood study examining the effects of environmental exposures on respiratory health and allergy development. All infants in the study had at least one parent with known allergies and were followed from infancy until age seven.