Inhaler Technique and Medication Adherence in COPD: Insights from a Nationwide Multicentre Study

Background Incorrect inhaler technique and poor adherence undermine COPD care, yet their joint determinants are incompletely defined. This study aimed to investigate the prevalence and determinants of critical inhaler errors and non-adherence, and their reciprocal association in COPD. Methods We conducted a nationwide multicentre cross-sectional study (July 2021–February 2022) in 10 tertiary outpatient pulmonary clinics across Turkey. Consecutive COPD patients aged ≥ 40 years using at least one inhaler for ≥ 3 months were included. Inhaler technique was assessed with device-specific checklists, and adherence with the Medication Adherence Report Scale–5 (MARS-5). Logistic regression was applied to identify independent predictors of critical errors and non-adherence. Results Among 358 patients (mean age, 66 years; 81% male), 39.7% had at least one critical error and 29.9% were non-adherent. Critical errors were associated with older age (adjusted OR [aOR], 1.04 per year; 95% CI, 1.01–1.08) and non-adherence (3.36; 1.83–6.18), and were less likely with prior inhaler training (0.23; 0.07–0.74) and uninterrupted medication access (0.32; 0.11–0.97). Non-adherence was less likely with dry-powder inhalers versus pressurised metered-dose inhalers (0.48; 0.28–0.82), prior training (0.38; 0.15–0.96), and uninterrupted access (0.35; 0.16–0.78), and more likely with any critical error (2.69; 1.62–4.46). Discrimination was acceptable (AUC, 0.75 for critical errors; 0.71 for non-adherence). Conclusions Inhaler misuse and medication non-adherence were common and bidirectionally associated. Standardised training and uninterrupted medication access independently lowered risk and represent high-leverage, implementable targets. Integration of digital adherence tools with routine education should be tested in pragmatic trials.