The course of asthma in preschool children with asthma

Background: Early-onset asthma constitutes an important but understudied asthma group. In addition, early diagnosis of asthma can be limited by difficulty in assessment of true disease. We investigated associations between asthma remission and predictors with a focus on age of asthma onset. Methods: Data was obtained from the Saskatchewan Health databases, which covers 99% of the population in Saskatchewan, Canada. We identified children with a diagnosis of asthma in the first 6 years of life and who had at least 10 years of follow-up after diagnosis (n=22,563). Of these, we included 6,393 children either with persistent asthma [≥ 1 physician visit or hospitalization for asthma (PVHA) at each year of follow-up] and those who had remission (had PVHA in the first year after diagnosis but at some point during the follow-up no longer receives healthcare through a PVHA until the end of the study). We used survival analysis to examine associations between remission and age of asthma onset [≤ 3 years (early-onset) and > 3 years (late-onset)]. Results: Of the study participants, 90.7% had early-onset and 9.3% had late-onset asthma. Over the 10 years of follow-up, 93.5% subjects had remission while 6.5% had persistent asthma. Early-onset asthma (HR = 1.10, 95%CI: 1.00–1.19), being female (HR = 1.12, 95%CI: 1.07–1.18), living in a rural (HR = 1.20, 95%CI: 1.13–1.27) and medium urban (HR = 1.17, 95%CI: 1.08–1.26) location were associated with remission. Conclusion: Asthma remission is more common in those with early-onset compared to those with late-onset asthma. The high proportion of early-onset asthma may reflect the difficulty in distinguishing asthma from other early life respiratory symptoms which may resolve during childhood.