Stability of Asthma Symptom Control in a Longitudinal Study of Mild-Moderate Asthmatics.

BACKGROUND: Achieving and maintaining symptom control is a primary goal of asthma management. Although factors associated with the likelihood of achieving symptom control have been studied, there are unanswered questions on the stability of symptom control, that is, the tendency of individuals to remain at a given symptom control level over time.

OBJECTIVE: The objective of this study was to evaluate the stability of symptom control using a longitudinal cohort of mild-moderate asthmatics.

METHODS: Participants reported symptom control using the Global Initiative for Asthma criteria at 5 assessments during the 1-year follow-up period. We described variability in the stability of symptom control between individuals, and used a random-effects logistic regression model to evaluate the impact of a suite of factors on the stability of symptom control.

RESULTS: A total of 429 individuals (67% female, mean age 51.6) contributed 2141 study visits. Individuals varied from completely stable in symptom control (18% remained at the same control level in all 5 visits) to completely unstable (12% changed the control level between all subsequent visits). Only 4% of between-individual variation in the stability of symptom control was explained by the included exposures, and a secondary analysis indicated that the history of symptom control stability was the best predictor of current stability.

CONCLUSIONS: The tendency to remain at a given control level varies significantly among patients with asthma. Only a small fraction of this variability is explained by observable characteristics. In the absence of predictors, a previous history of symptom control stability is the best indicator of future stability and should be considered when monitoring symptom control.