Childhood asthma has 4 longitudinal asthma trajectories, which are defined based on frequency of asthma exacerbations and asthma medication ranks, according to study findings published in the Annals of Allergy, Asthma, & Immunology.
Researchers sought to investigate longitudinal asthma trajectories based on the exacerbation frequency throughout childhood and level of asthma medication used, based on data from the Korean Childhood Asthma Study, a nationwide, prospective, and observational cohort of children with asthma.
The current analysis was based on data from 531 children aged 7 to 10 years diagnosed with asthma from the Korean Childhood Asthma Study. The study recorded the history of asthma medications used from 6 to 12 years of age. Asthma exacerbations, defined as the use of a systemic corticosteroid for at least 3 days during a visit to the hospital or clinic, were recorded from birth to 12 years of age. An asthma medication rank was assigned to each child; this rank was determined by the yearly sum of prescribed asthma medications based on the recommended step therapy from the Global Initiative for Asthma (GINA) guidelines for children 6 to 12 years of age.
The researchers identified 4 longitudinal asthma trajectories based on lowest Bayesian information criterion:
- cluster 1 (n=43): lesser exacerbation with low-step treatment;
- cluster 2 (n=163): lesser exacerbation with middle-step treatment;
- cluster 3 (n=30): highly frequent exacerbations in early childhood with small-airway dysfunction; and
- cluster 4 (n=295): frequent exacerbations with high-step treatment.
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Small-airway dysfunction in children with frequent wheeze in early life may result from complex interactions between viral infection, airway epithelial immunity, host genetic predisposition, and immune responses.
At baseline, patients in cluster 1 experienced a mean (SD) of 0.8 (0.3) exacerbations a year vs 1.5 (1.6), 0.3 (0.1), and 0.2 (0.1) in clusters 2, 3, and 4, respectively. Compared with those in cluster 4, patients in cluster 3 had more frequent asthma exacerbations (mean [range], 1.5 [0.2-1.0] per year vs 0.8 [0.16-6.20] per year; P <.001) and the greatest history of acute bronchiolitis during the first year of life (66.7% vs 36.6%; P =.002). Notably, cluster 3 included preschool children with a viral wheeze in infancy, who later developed childhood asthma with recurrent wheeze due to previous respiratory infections.
Patients in cluster 3 experienced the highest rates of bronchiolitis in the first 12 months (66.7%) compared with clusters 1, 2, and 4 (27.9%, 34.4%, 36.6%, respectively) and the lowest levels of maximal mid-expiratory flow z score. Patients in cluster 4 (mean, 25.74 ppb) had the highest fractional exhaled nitric oxide (FeNO) levels compared with those in other clusters (16.75 ppb for cluster 1; 23.95 ppb for cluster 2; 19.87 ppb for cluster 3), although the most significant difference was observed between clusters 1 and 4.
Patients in cluster 4 had the highest prevalence of allergic rhinitis in the preceding 12 months (80.3%) compared with clusters 1 through 3 (58.1% vs 70.6% vs 76.7%, respectively), whereas patients in cluster 1 experienced the highest rate of asthma remission in the preceding 12 months at 12 years of age (90.7%), followed by clusters 2 through 4 (74.2% vs 63.3% vs 51.9%, respectively).
There were no significant differences in the prevalence of atopy across groups.
Study limitations include differences in the periods of exacerbation frequency vs medication ranking; non-inclusion of off-label medications in the medication ranks; and the relatively short study period for conducting a longitudinal study.
“Small-airway dysfunction in children with frequent wheeze in early life may result from complex interactions between viral infection, airway epithelial immunity, host genetic predisposition, and immune responses,” study authors concluded. They noted that study results offer important information for developing potential therapeutic targets for treating childhood asthma.
