Long-term adherence to inhaled corticosteroids: does it make a difference for asthma control?

Abstract

Background: Chronic conditions often require continued daily use of medication, yet adhering to these regimens is difficult to sustain long-term. In asthma, inhaled corticosteroids (ICs) help achieve and maintain asthma control but ICs adherence is suboptimal. Evidence is scarce regarding its long-term dynamics and role in managing asthma. We examined the longitudinal variation of ICs adherence and its effects on asthma control. Methods: A prospective cohort of persistent asthma patients (12-40 yrs) in France and the United Kingdom were followed up for 24 months by 4-monthly computer-assisted telephone interviews (CATIs), assessing ICs adherence and asthma control. We used longitudinal multilevel models to predict the risk of uncontrolled asthma based on within and between-patient variations in adherence, and patient and treatment characteristics. Findings: In 2416 CATIs from 542 patients (mean age 269 years, 53% women, 85% French), 33% used <60%, 14% 60-80%, 24% >80% of prescribed ICs; 29% were fully adherent. During follow-up, 111 patients maintained asthma control, and 151 remained uncontrolled; 135 maintained >80% adherence, and 131 remained below 80%. Patients with higher average adherence were less likely to report uncontrolled asthma (OR=0.70[0.56-0.86], p<.001), as were male patients (OR=0.60[0.40-0.92], p<.05). Higher baseline asthma severity and add-on therapies predicted uncontrolled asthma (OR=1.88[1.46-2.42], p<.001; OR=1.64[1.03-2.61] and 2.57[1.06-6.24], p<.05). Within-person adherence variation was unrelated to asthma control. Discussion: High adherence and good control proved difficult to achieve or maintain long-term. Between-person results suggest a protective effect of sustained adherence in managing asthma. The dynamic interplay between adherence and asthma control requires further investigation.