Inhaler adherence, associated factors and outcomes among adult asthma patients in Singapore

Inhaler therapy is paramount in asthma management, yet non-adherence poses a significant challenge. This study investigates inhaler adherence patterns among adult asthma patients, employing the Test of Adherence to Inhalers (TAIs) questionnaire.

This cross-sectional study recruited 99 eligible patients from a specialist outpatient clinic over six months. The TAI questionnaire was administered to the patients. Data on asthma control test scores, medication possession ratio, and healthcare utilisation were collected. Statistical analyses were performed to examine the associations between adherence, patient characteristics, and clinical outcomes.

More than half of the patients (68.7%) exhibited intermediate ( n = 23) or poor ( n = 45) adherence, with younger age associated with poorer adherence. Different patterns of non-compliance were identified; 38.8% ( n = 19) of patients with poor adherence showed deliberate non-compliance, whereas only 7.3% ( n = 3) with good adherence showed unconscious non-compliance. Surprisingly, patients with intermediate and poor adherence often achieved good asthma control, revealing potential challenges in outcome-based adherence assessments. A relatively higher but statistically non-significant proportion of patients with poor adherence had at least one hospitalisation or emergency department attendance due to asthma (42.2% with poor adherence vs. 35.5% with good adherence) or at least one asthma exacerbation requiring oral corticosteroid (64.4% with poor adherence vs. 48.4% with good adherence) in the past 12 months.

This study provides insights into inhaler adherence among local adult asthma patients, identifying distinct adherence patterns and recognising potential complacency issues associated with traditional adherence assessments. Despite these limitations, our findings contribute to the optimisation of asthma care through a nuanced understanding of inhaler adherence.