Long-term adherence to inhaled corticosteroids and asthma control in adult-onset asthma

Background In short-term studies, poor adherence to inhaled corticosteroids (ICS) has been associated with worse asthma control, but the association of long-term adherence and disease control remains unclear. Objective To assess the relationship between 12-year adherence to ICS and asthma control in patients with adult-onset asthma. Methods As part of the Seinajoki Adult Asthma Study, 181 patients with clinically confirmed new-onset adult asthma and regular ICS medication were followed-up for 12 years. Adherence (%) to ICS was assessed individually ((µg dispensed/µg prescribed)×100) during the follow-up. Asthma control was evaluated after 12 years of treatment according to the Global Initiative for Asthma 2010 guideline. Results Asthma was controlled in 31% and not controlled (partly controlled or uncontrolled) in 69% of the patients. Patients with not-controlled asthma were more often male, older, nonatopic and used higher doses of ICS than those with controlled disease. The mean±sd 12-year adherence to ICS was 63±38% in patients with controlled asthma and 76±40% in patients with not-controlled disease (p=0.042). Among patients with not-controlled asthma, those with lower 12-year adherence (<80%) had more rapid decline in forced expiratory volume in 1 s (-47 mL·year-1) compared to patients with better adherence (≥80%) (-40 mL·year-1) (p=0.024). In contrast, this relationship was not seen in patients with controlled asthma. Conclusions In adult-onset asthma, patients with not-controlled disease showed better 12-year adherence to ICS treatment than those with controlled asthma. In not-controlled disease, adherence <80% was associated with more rapid lung function decline, underscoring the importance of early recognition of such patients in routine clinical practice.