Relationship of inhaler adherence behaviour to clinical outcomes in copd: an observational study

COPD remains a leading cause of healthcare use despite the availability of effective inhaled therapies. We examined adherence to maintenance therapy by assessing the key components of good inhaler use: habit of use and inhaler technique. The relationship between adherence patterns, specific patient characteristics and clinical outcomes at one year was examined. We recruited 226 hospitalised patients with a diagnosis of COPD to this prospective observational study. Inhaler adherence was remotely monitored for 90 days after hospital discharge using an INCA TM audio recording device. Cluster analysis grouped patients by their adherence behaviour based on the mean rate of attempted use and critical technique errors. The clinical and psychosocial characteristics of each cluster were examined. The rate of all–cause mortality and healthcare use at 12 months was recorded. Survival analysis was used to evaluate the time to first event across adherence groups. Adherence data was available for 195 patients. We identified four patterns of Adherence behaviour: (1) Regular habit of use and good technique (28%); (2) Regular habit of use and poor technique (21%); (3) Poor habit of use and good technique (33%); (4) Poor habit of use and poor technique (19%). The overall event rate was lowest in Cluster 1, 5.46/person/year. Cluster 2 had the lowest annual rate of hospital presentation, but accounted for the majority of community prescriptions for antibiotics and steroids, mean 4.6/person/year. In an adjusted Cox regression model, Cluster 3 had an increased risk of any adverse outcome compared to Cluster 1, Hazard Ratio 1.8 (1.1–2.9), p=0.02. This group were notable for high anxiety scores and mild cognitive impairment. There was a stepwise increase in mortality across groups, from 11% in Cluster 1% to 33% in Cluster 4, p