António Duarte-de-Araújo, Pedro Teixeira, Venceslau Hespanhol, Jaime Correia-de-Sousa

Adherence to inhaled medications by COPD patients is a challenging issue, but relatively understudied. The aim of this study is the characterization of adherence to inhaled medications by COPD patients, with a focus on patient-related determinants. Stable COPD outpatients ≥40 years of age from a respiratory unit and diagnosed according to the Global Initiative for Chronic Obstructive Lung Disease criteria were included in a cross-sectional study. The Measure of Treatment Adherence (MTA), the Beliefs about Medications Questionnaire (BMQ) and demographic, clinical, and COPD questionnaires were used. After completing these questionnaires, semi-structured interviews were carried out and participants were encouraged to justify their opinions and behaviors. Field notes were made during the interviews and each interview was analyzed before the next one. Quantitative and qualitative analyses of the variables were then performed. A total of 300 out of 319 participants (mean age =67.7 years, 78.1% males) completed the MTA questionnaire. Of these, 31.3% were considered poorly adherent and 16.7% as non-adherent to the inhaled therapy. A statistically significant negative association was found between adherence and current smoking status (P=0.044), and between adherence and FEV1% (P=0.000). The mean BMQ Necessity score was higher in adherent patients (P=0.000), but the the mean Concern score was similar for both (P=0.877). We found nine patterns of poor-adherence, six reasons given for poor-adherence behaviors, five reasons for good-adherence behaviors and three patient-related domains on adherence to medications. Adherence is related to need perception and to the functional severity of the disease. A non-adherent patient is usually a current smoker with lower degree of airflow limitation and lower perception of medication necessity. New information obtained was related to the patterns and reasons for different adherence behaviors, which are based on three major groups of patient related-determinants: health-related experiences, health-related behaviors and health-related beliefs.