Longitudinal Patterns and Patient-Reported Barriers to Maintenance Inhaler Adherence in COPD: A Three-Wave...

To describe short-term patterns of maintenance inhaler adherence and patient-reported barriers among adults with chronic obstructive pulmonary disease (COPD), and to examine whether barriers documented at earlier follow-ups were associated with subsequent adherence.

This single-center longitudinal observational study included 278 adults with COPD followed at approximately 1-month intervals for three waves. Adherence was classified from patient- or caregiver-reported inhaler use obtained through routine semi-structured follow-up during the preceding month; unclear or unassessed use was coded missing. Transparent text rules identified five barrier categories and were validated against independent review of 150 randomly sampled records. The primary temporally ordered analysis used Firth logistic regression to compare Wave 3 low adherence between participants with any barrier documented during Waves 1-2 and those with none. Barrier-category count, adjacent-wave models, contemporaneous generalized estimating equations, and inverse probability-of-observation weighting were secondary or sensitivity analyses.

Adherence was evaluable for 264, 247, and 236 participants at Waves 1, 2, and 3; high adherence was recorded in 259 (98.1%), 222 (89.9%), and 189 (80.1%), respectively. Medication beliefs/perceived effectiveness were the most frequently documented barrier across any wave (35/278, 12.6%). In the primary analysis, any barrier documented during Waves 1-2 was associated with low adherence at Wave 3 compared with no prior barrier (adjusted odds ratio [OR] 4.29, 95% confidence interval [CI] 2.00-9.16). The corresponding result using truncated stabilized observation weights was OR 4.81 (95% CI 2.20-10.50). In a supportive Wave 2→3 model, current high adherence was associated with next-wave high adherence (OR 19.55, 95% CI 3.03-284.84), whereas individual barrier estimates were imprecise.

High adherence was recorded less frequently at later follow-ups, and the presence of a previously documented barrier was associated with low adherence at Wave 3. These observational findings do not establish causation or individual prediction.