Association between asthma control trajectories in preschoolers and disease remission.

Introduction Early disease morbidity has been associated with asthma persistence in wheezing preschoolers; however, whether asthma control trajectories shortly after diagnosis could influence remission is unknown. We examined the association between asthma control trajectories 2 years post-diagnosis in preschoolers and subsequent disease remission. Methods We conducted a multicenter population-based retrospective cohort study consisting of 48 687 children with asthma diagnosed before 5 years old and born between 1990 and 2013 in 4 Canadian provinces who had prolonged disease activity post-diagnosis. Prolonged disease activity was defined as ≥1 medical visit or medication for asthma every 6-month period for ≥4 of the 6 periods post-diagnosis. Follow-up began at 3 years post-diagnosis (at cohort entry). Remission was defined as two consecutive years without drug claims or medical visits for asthma or asthma-like conditions following cohort entry. Asthma control trajectories, ascertained over four 6-month periods following diagnosis using a validated index, were classified as: controlled throughout, improving control, worsening control, out-of-control throughout, and fluctuating control. Adjusted Cox models estimated associations between asthma control trajectories and time-to-remission. A random-effects meta-analysis summarised province-specific Hazard Ratios (HRs). Results The pooled remission rate was 8.91 (95%CI 8.80,9.02)/100 person-years. Compared to children controlled throughout, poorer asthma control was associated with incrementally lower HRs (95%CI) of remission in 4 other trajectories: improving control, 0.89 (0.82,0.96); fluctuating control, 0.78 (0.71,0.85); worsening control, 0.68 (0.62,0.75); out-of-control throughout, 0.52 (0.45,0.59). Conclusions Asthma control trajectories 2 years following a diagnosis in preschool were associated with remission, highlighting the clinical relevance of documenting control trajectories in early life.