Determinants of self-reported adherence to inhaler therapy in patients with chronic obstructive pulmonary disease

BACKGROUND: Adherence to therapy is crucial for COPD patients, since non-adherence leads to worse quality of life, increased health-care expenditure and poor clinical outcome. The aim of this study was to identify the main determinants of suboptimal adherence to therapy in a cohort of COPD patients. METHODS: General information (age, BMI, smoking, comorbidities, education, life style), lung function, exacerbations, symptoms and COPD treatment were collected. Adherence to therapy was assessed by self-reported 4-item Morisky Medication Adherence Scale (MMAS-4), and was related to anthropometric, socio/economic and health status data, obtained by questionnaires (COPD Assessment Test, CAT; Treatment Satisfaction Questionnaire, HRQoL; Katz Index of Independence of Daily Living Activities, Lawton Instrumental Activities of Daily Living Scale). RESULTS: 136 COPD patients were studied (age 72±8 yrs; 73.5% men; BMI 28.5±7.4 kg/m(2); FEV(1) 53.5±19.0 % predicted). Nearly half of the patients (46.3%) had suboptimal adherence to therapy (score >0) and, as compared to those with optimal adherence, had higher prevalence of women and coronary artery disease, heavier smoking history and worse CCQ overall score. The results of multivariate analysis showed that the determinants of suboptimal adherence were female sex (OR 4.339, 95%CI 1.509-12.474, p=0.006), amount of pack/years smoked (OR 1.947, 95%CI 1.141-3.323, p=0.015), higher CCQ overall score (OR 3.318, 95%CI 1.050-9.892, p=0.049) and higher education (OR 2.758, 95%CI 1.083-7.022, p=0.033). Adherence was better in patients assuming triple inhaler therapy. CONCLUSIONS: Suboptimal adherence is frequent among COPD patients, particularly in women, heavy smokers and subjects with high educational level. Interventions to improve adherence should be especially addressed to patients with these characteristics.