Prevalence and Potential Risk Factors for T2-Low Asthma Among School-Aged Children in the National Health and Nutrition Examination Survey, 2007-2012.

BACKGROUND

T-helper 2 (T2)-high asthma has been assumed to be the most common asthma endotype in school-aged youth.

OBJECTIVE

To assess the prevalence and potential risk factors for T2-low asthma in a representative sample of U.S. children.

METHODS

Cross-sectional study of 4,284 children aged 6 to 17 years in the 2007-2012 National Health and Nutrition Examination Survey (NHANES). Using available biomarkers, T2-low asthma was defined by an absolute peripheral blood eosinophil count (AEC) lower than 300 cells/μL, and fractional exhaled nitric oxide (FeNO) less than 25 ppb; T2-high asthma was defined by AEC of 300 cells/μL or greater or FeNO 25 ppb or greater. In a secondary analysis, an AEC lower than 428 cells/μL and a FeNO lower than 32.5 ppb was used to define T2-low asthma. Multinomial logistic or linear regression was used for the multivariable analysis.

RESULTS

Among 505 children with asthma, 231 (45.7%) had T2-low asthma. Compared with controls, those with T2-low asthma were 1.1- to 2.1-times significantly more likely to be older, female, and overweight or obese. Children with T2-high asthma were more likely than controls to be male and non-Hispanic Black and to have vitamin D insufficiency and bronchodilator responsiveness. Children with either asthma subtype were more likely than controls to have a family history of asthma, hay fever episodes in the prior year, and lower %predicted forced expiratory volume in 1 second (FEV) and FEV/FVC (forced vital capacity). In the secondary analysis, current second-hand smoke exposure was also associated with T2-low asthma.

CONCLUSIONS

Overweight was associated with T2-low asthma, whereas non-Hispanic Black race and vitamin D insufficiency were associated with T2-high asthma in this study of U.S. children.