Background: Adherence to inhalation therapy is a critical determinant of the success of asthma management. Reasons for nonadherence have been well studied, but reasons for good adherence are poorly understood. Understanding the mechanisms of adherence to inhalation therapy is important in developing strategies to promote adherence. The objective of this study was to assess the factors and mechanisms that contribute to and the clinical outcomes relating to adherence to inhalation therapy.
Methods: The factors and outcomes related to adherence to inhalation therapy were examined cross-sectionally in 176 adults with asthma using a self-reported adherence questionnaire that consisted of four items dealing with the use of inhaled controller medications. A 5-point Likert scale was used for the responses to each item. Adherence was assessed based on the overall mean adherence score.
Results: Of the 176 patients who were potential participants, 146 (83%) responded with usable information. Significant factors associated with the overall mean adherence score were older age (r = .18, p = .032) and receiving repeated instruction on inhalation techniques (p = .0016). Of the 146 respondents, 25 (17.1%) patients were given repeated verbal instruction or demonstrations of inhalation technique by a respiratory physician. On logistic regression analysis, good adherence to inhalation therapy was significantly related to the receiving of repeated instruction on inhalation technique, with an odds ratio of 2.90 (95% confidence interval 1.07-7.88; p = .037). Furthermore, less intentional nonadherent behavior was reported in patients with repeated instruction on inhalation technique compared to those without it. A significant correlation was found between the overall mean adherence score and the frequency of asthma exacerbations (r = -.19, p = .021), emergency room visits (r = -.19, p = .042), and the health-related quality of life score (St. George's Respiratory Questionnaire: Total, r = -.22, p = .024; Symptoms, r = -.21, p = .022; Impacts, r = -.20, p = .035).
Conclusions: Repeated instruction on inhalation techniques may contribute to adherence to inhalation therapy through decreasing intentional nonadherence. Furthermore, good adherence to the therapeutic regimen may offer good asthma-related outcomes.