Lung Defects More Common in Girls Than in Boys at Risk for Asthma

Barbara Boughton

April 13, 2011

April 13, 2011 (San Francisco, California) — Lung defects in children who are at risk for asthma or allergies because of family or personal medical history are far more likely to occur in girls than in boys, according to researchers here at the American Academy of Allergy, Asthma and Immunology 2011 Annual Meeting.

They conducted a study with a novel noninvasive magnetic resonance imaging (MRI) technique, known as helium-3 MRI, in which patients inhale hyperpolarized helium, a harmless gas, which lights up in MRI images, revealing areas in the lungs that are well ventilated. The researchers found that that 9- and 10-year-old girls had significantly more lung defects than boys of the same age, whether or not they had asthma.

The study's findings might eventually help researchers understand the biologic mechanisms that lie behind sex differences in asthma symptom expression, according to researcher Daniel Jackson, MD, assistant professor of pediatric allergy and immunology at the University of Wisconsin, Madison.

The researchers looked at and scored defects on the helium-3 MRIs of lungs in a cohort of 9- and 10-year-old girls and boys from the Childhood Origins of Asthma Study (COAST), which seeks to provide insights into the development of allergies and asthma. Scores were based on the size and number of lung defects seen on the images. Although those with asthma had higher defect scores than those who had not been diagnosed with the disease, the researchers found that there were also clear sex differences. They hope that such sex differences will provide clues as to why asthma symptoms are more common in boys than in girls, but why women are more prone to asthma as adults than men.

"We'll be following and performing imaging again on these same children at ages 12 and 13 to see whether these defects persist over time. We also want to see whether the severity of the defects relate to the expression of the asthma phenotype in males and females," Dr. Jackson said.

In the study, helium-3 MRIs were used to image the location and size of areas of the lungs with no air flow in 43 children from COAST. Seventeen of these children had a diagnosis of asthma but were under treatment for symptom control.

The researchers also assessed how well the children performed on spirometry and sought to ascertain whether higher lung defect scores were associated with a history of rhinovirus in infancy.

To their surprise, higher defect scores did not correlate with either rhinovirus history or spirometry scores, according to researcher Elizabeth Anderson, RN, a research coordinator at the University of Wisconsin, Madison. "When the children are scanned after puberty, we'll be looking at the differences in lung development among boys and girls, and how it is affected by hormonal changes," she said. The researchers might also be able to assess whether remodeling or inflammation contributes to lung defects — information that could lead to improved prognosis of asthma and determination of treatment, Ms. Anderson said.

"This study does suggest that lung defects may be related to developmental issues," said Mitchell Grayson, MD, associate professor of pediatrics, medicine, microbiology, and molecular genetics at the Medical College of Wisconsin, in Milwaukee. However, "even if there are these sex differences, it's not something that will have an impact on clinical practice now; it doesn't really give you more information than we already have on asthma patterns," he said.

"The bigger issues that will be important to assess when these kids get older are: Do the sex differences in lung defects go away, and how might these insights affect treatment?" he said.

Dr. Jackson, Dr. Grayson, and Ms. Anderson have disclosed no relevant financial relationships.

American Academy of Allergy, Asthma and Immunology (AAAAI) 2011 Annual Meeting: Abstract 504. Presented March 20, 2011.


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