Risk Factors for Poor Adherence to Inhaled Corticosteroid Therapy in Patients With Moderate to Severe Asthma

Background Poor adherence to inhaled corticosteroid (ICS) therapy is a common reason for worsened asthma control. Objective We investigated the characteristics of patients with moderate to severe asthma who showed poor adherence to therapy, to identify the barriers for optimal ICS therapy in a real-world observational cohort. Methods We enrolled patients aged ≥20 years presenting with moderate to severe asthma who were enrolled at 18 hospitals in Japan. According to the Global Initiative for Asthma 2018 steps 3-5, the patients were considered as moderate to severe asthmatic. At inclusion, clinical information was obtained using a self-completed questionnaire. Poor adherence was defined as skipping the ICS therapy for more than once a week or inability to recognize the necessity of daily ICS therapy. Adherence Starts with Knowledge 20 (ASK-20) questionnaire was used to evaluate the cause of therapy incompliance. Results Of the total 85 participants, 19 (22%) showed poor adherence. The median age at diagnosis in the poor adherence group was 10.0 years (interquartile range [IQR], 3.0-50.0), and that in the good adherence group was 41.0 years (18.5-51.5; P = 0.050). The scores for the ASK-20 items related to the "resistance to taking too much medicine" and "compliance with the number of dosing" demonstrated statistically significant differences between patients diagnosed with asthma during their childhood and others. Conclusions Age at diagnosis is an independent risk factor to predict poor ICS adherence among adults with moderate to severe asthma.