Background:
Daily nebuliser use is crucial for people with cystic fibrosis (CF) to stay healthy, but average adherence is only 35-50%. Making nebuliser use ‘habitual’ (i.e. automatic) may aid adherence, but extant CF literature has mainly focused on treatment burden and factors involving conscious deliberation. This thesis aims to explore a broad range of clinical and psychological factors that are potentially associated with objective nebuliser adherence among adults with CF.
Methods:
This thesis encompassed three studies. First, a retrospective analysis of adherence data captured using chipped nebulisers from 2013-2016 among 126 adults was performed to explore relevant clinical factors. Second, a mixed-methods study was performed among 20 adults to identify the psychological factors differentiating high or low nebuliser adherence patterns (i.e. ≥80% or <50% of all nebulised treatments over one year). Third, a secondary quantitative analysis was performed using data from a two-centre pilot adherence trial among 64 adults to replicate findings from the mixed-methods study.
Results:
The retrospective analysis showed a U-shape relationship between adherence and age, with lowest adherence levels among adults aged 19-25 years. Lower adherence was also noted for long term (>3 months) nebuliser regimen in comparison to shorter-term treatments.
The mixed-methods study found stronger habit and greater opportunities among high adherers, though habit and perceived opportunity scores were highly positive correlated. Habit attenuated the relationship between treatment complexity and perceived treatment burden. Indeed, in interviews, high adherers reported that routinisation and greater automaticity made treatment burden more manageable.
The secondary analysis using pilot trial data found stronger habit and lower concerns among high adherers. In an ordinal regression model, only habit strength was independently associated with adherence.
Conclusion:
Adherence to long-term CF nebuliser treatments is problematic, especially among younger adults with CF. Habit may attenuate perceived burden and is a promising target for adherence interventions.
