Asthma controller medication adherence, risk of exacerbation, and use of rescue agents among Texas medicaid patients with persistent asthma

Abstract

Background: Adherence to asthma long-term controller medications is one of the key drivers to improve asthma management among patients with persistent asthma. While suboptimal use of controller medications has been found to be associated with more frequent use of oral corticosteroids (OCS), few studies exist regarding the relationship between adherence to controller therapy and the use of short-acting beta2-agonists (SABAs). A better understanding of the association between adherence to asthma controller agents and use of reliever medications will help health care providers and decision makers enhance asthma management. Objective: To determine if there is a relationship between asthma controller adherence, risk of exacerbation requiring OCS, and use of asthma rescue agents. Methods: Texas Medicaid claims data from January 1, 2008, to August 31, 2011, were retrospectively analyzed. Continuously enrolled patients aged 5-63 years with a primary diagnosis of asthma (ICD-9-CM code 493) and with 4 or more prescription claims for any asthma medication in 1 year (persistent asthma) were included. The index date was the date of the first asthma controller prescription, and patients were followed for 1 year. The primary outcome variables were SABA (dichotomous: < 6 vs. = 6) and OCS (continuous) use. The primary independent variable was adherence (proportion of days covered [PDC]) to asthma long-term controller medications. Covariates included demographics and nonstudy medication utilization. Multivariate logistic and linear regression analyses were employed to address the study objective. Results: The study sample (n = 32,172) was aged 15.0 ± 14.5 years, and adherence to controller therapy was 32.2% ± 19.7%. The mean number of SABA claims was 3.7 ± 3.1, with most patients having 1-5 claims (73.2%), whereas 19.4% had ≥ 6 SABA claims. The mean number of OCS claims was 1.0 ± 1.4. Adherent (PDC ≥ 50%) patients were 96.7% (OR = 1.967; 95% CI = 1.826-2.120) more likely to have ≥ 6 SABA claims when compared with nonadherent (PDC < 50%) patients (P < 0.001). As for OCS use, adherent patients had 0.11 fewer claims compared with nonadherent patients (P < 0.001). Importantly, patients with ≥ 6 SABA claims had 0.7 more OCS claims compared with patients with < 6 claims for SABA (P < 0.001). The odds of having ≥ 6 SABA claims were higher for concurrent dual therapy users, older age, males, African Americans and higher number of nonstudy medications (P < 0.001). Dual therapy users, younger age, Hispanic ethnicity, and higher number of nonstudy medications were associated with an increase in OCS use (P < 0.005). Conclusions: Adherence to long-term controller medications was suboptimal among patients with asthma. Adherent patients had fewer OCS claims, indicating that adherence to controller therapy is critical in preventing asthma exacerbations requiring OCS use. Although there was a positive relationship between adherence to long-term controller medication and SABA use, increased SABA use served as a predictor of increased OCS use, which indicates poor asthma control. Health care providers should be aware of OCS and SABA use among patients who are both adherent and nonadherent to asthma controller medications.