4–year trajectory of medication adherence amongst severe asthma patients: Risk factors and impact on asthma control

Abstract

Non-adherence to therapy contributes to poor asthma control. However, there is paucity of data about long term adherence in adult severe asthma and impact on control. Aim to identify medication adherence patterns amongst adult severe asthma patients, risk factors for poor adherence, and its impact on asthma control over a 4-year period. From 2011-2015,107 patients on Step 4/5 of GINA were identified in a severe asthma clinic. Adherence was quantified using the medication possession ratio(MPR). Group based trajectory modelling was used to identify adherence patterns over 4 years. Adherence was defined as: good(MPR >0.6), fair(MPR 0.5-0.6) and low(MPR There were 4 trajectory groups:(1) low adherence which worsened within a year (n=23),(2)consistently low adherence (n=15),(3) consistently fair adherence (n=56),(4)good adherence with slight decline over 4 years (n=13). No differences in onset age, gender, race, smoking, prevalence of anxiety / depression, and lung function were found between groups. 75.7% required asthma counselling, but less frequently in Group 4(53.8%, p=0.013). At baseline, overall median daily inhaled Fluticasone equivalent dose was 500mcg/day. At year 4, Group 4 had a lower median daily dose(320mcg/day)compared to Groups 1(490mcg/day),2 (640mcg/day) and 3(640mcg/day) (p=0.008). No differences in baseline ACT scores(p=0.793), change in ACT scores(p=0.237), emergency visits(p=0.688)or admissions(p=0.740)were noted between groups. Baseline characteristics did not identify long term adherence patterns in severe asthma, which were stable or worsened over time. Good adherence resulted in asthma control with lower doses of inhaled corticosteroids.