Factors associated with adherence to inhaled medicines in cystic fibrosis following the introduction of elexacaftor/tezacaftor/ivacaftor using electronically captured adherence data.

BACKGROUND

Use of inhaled medicines by people with cystic fibrosis (pwCF) has declined since the introduction of CFTR modulators such as elexacaftor/tezacaftor/ivacaftor (ETI). Inhaled medicines may still benefit those with established lung disease. This study explored factors associated with adherence to inhaled medicines across a cohort of pwCF.

METHODS

In this cross-sectional, observational study, all adults with CF (≥16 years) eligible for inhaled medicines at a single UK CF centre were included. Between July 2023 and August 2024, data were extracted from local medical records on 25 factors across four categories: demographic, socio-economic, health-related, and treatment-specific psychological factors (e.g. habit score, treatment necessity beliefs). Mean percent adherence, captured electronically via data-logging nebuliser devices, over the preceding 12 months was the outcome in a multivariable linear regression analysis.

RESULTS

Of 240 pwCF on the centre's caseload, 214 (88%) were eligible and 190 of these (89.2%) were prescribed a CFTR modulator. Mean adherence to inhaled medicines was 26.4% (95% CI 22.2-30.7%). In multivariable analysis, adherence was significantly associated with habit score, socio-economic status, treatment regimen complexity, neurodivergence, and age. Habit score explained the greatest variance (adjusted partial R² = 0.21). Those with the strongest habit for taking inhaled medicines had a mean adherence of 41.7% (34.7-47.3%), versus 11.7% (7.6-15.8%) in those with low/absent habit.

CONCLUSION

Habit continues to have an important association with adherence to inhaled medicines in the ETI era. Further studies are required to understand the role of habit-based interventions to support adherence among pwCF in the ETI era.