Men From Mars, Women from Venus for Severe Asthma Risk

Opposite relationships seen between childhood weight and later asthma admissions

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• This research was published as an abstract and presented at a meeting. The findings should be considered preliminary until published in a peer-reviewed journal.

LONDON -- Overweight girls showed an increased risk for developing severe asthma in early adulthood in a large registry study, but for boys, it was the opposite: being underweight as a child was tied to the most risk for developing severe asthma later, researchers said here.

The association between childhood body mass index (BMI) and hospital admission for asthma in early adulthood was found to be U-shaped in an analysis of school health exam records from Denmark which included more than 300,000 children followed to adulthood.

"We were not surprised to find that being overweight during childhood increased severe asthma risk in women, but we also expected to find this in men," researcher Charlotte Suppli Ulrik, MD, of Hvidovre Hospital and the University of Copenhagen, Denmark, told MedPage Today.

Women who were overweight during childhood had a 39% increased relative risk (versus normal weight) for asthma-related hospital admission during early adulthood, while men who were underweight as children had a 24% increased risk for asthma admissions.

Ulrik presented the findings here at the European Respiratory Society International Congress 2016.

The researchers analyzed data from the Copenhagen School Health Records Registry, which included all children between the ages of 7 and 13 attending school in the city.

Ulrik explained that from the 1930s until the late 1980, all children enrolled in school underwent compulsory annual physical exams, which included measurement of height and BMI.

These data were matched to the Danish National Patient Registry, which was used to identify asthma admissions to hospital during adulthood.

Cox-regression analysis was used to assess the association between childhood BMI z-score and asthma admissions.

During 5,101,123 person-years of follow-up, 1,962 incident asthma admissions were recorded.

The researchers performed a further risk estimation which included participants categorized by childhood BMI z-scores into the lower quartile, interquartile, and upper quartile ranges.

Among the study findings:

• Risk of an asthma admission during early adulthood was significantly higher for women who were overweight as children, compared to women who were underweight (hazard ratio at age 13, 1.39, 95% CI 1.20 to 1.60)
• Men who were underweight during childhood had a higher risk of an asthma-related hospital admission in early adulthood than men whose BMI was in the normal range during childhood (HR at age 12, 1.24, 95% CI 1.03 to 1.49)

"Our findings present an intriguing look at the differences we see between men and women when we identify predictors of asthma among children," Ulrik said.

She told MedPage Today that several factors could explain the gender differences between childhood BMI and later asthma risk observed in the study.

She noted that non-allergic asthma is common among obese girls and women who develop asthma, while allergic asthma is common among boys.

"This might have something to do with it, and so might (gender differences in) lung mechanics and activity levels," she said. "There are a lot of possible explanations, but to be honest we really don't know."

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