The impact of adherence to inhaled drugs on 5‐year survival in COPD patients: a time dependent approach
PURPOSE
Whether inhaled medications improve long-term survival in Chronic Obstructive Pulmonary Disease (COPD) is an open question. The purpose of this study is to assess the impact of adherence to inhaled drug use on 5-year survival in COPD.


METHODS
A population-based cohort study in three Italian regions was conducted using healthcare linked datasets (hospitalization, mortality, drugs). Individuals (45+ years) discharged after COPD exacerbation in 2006-2009 were enrolled. Inhaled drug daily use during 5-year follow-up was determined through Proportion of Days Covered on the basis of Defined Daily Doses. Five levels of time-dependent exposure were identified: (i) long-acting β2 agonists and inhaled corticosteroids (LB/ICS) regular use; (ii) LB/ICS occasional use; (iii) LB regular use; (iv) LB occasional use; and (v) respiratory drugs other than LB. Cox regression models adjusted for baseline (socio-demographic, comorbidities, drug use) and time-dependent characteristics (COPD exacerbations, cardiovascular hospitalizations, cardiovascular therapy) were performed.


RESULTS
A total of 12 124 individuals were studied, 46% women, mean age 73,8 years. Average follow-up time 2,4 year. A total of 3415 subjects died (mortality rate = 11.9 per 100 person years). In comparison to LB/ICS regular use, higher risks of death for all remaining treatments were found, the highest risk for respiratory drugs other than LB category (HR = 1.63, 95%CI 1.43-1.87). Patients with regular LB use had higher survival than those with LB/ICS occasional use (HR = 0.89, 95%CI 0.79-0.99).


CONCLUSIONS
These findings support clinical guidelines and recommendations for the regular use of inhaled drugs to improve health status and prognosis among moderate-severe COPD patients. © 2016 The Authors. Pharmacoepidemiology and Drug Safety Published by John Wiley & Sons Ltd.