An observational study examining the effect of comorbidity on the rates of persistence and adherence to newly initiated oral anti‐hyperglycaemic agents

PURPOSE: To examine whether the type of comorbid condition affects medication persistence and adherence in patients initiating oral anti-hyperglycaemic (OAH) therapy. METHODS: The Irish Health Services Executive pharmacy claims database was used to identify a cohort of incident OAH therapy users (anatomical therapeutic chemical A10B), ≥25 years, between June 2009 and December 2010. Persistence and adherence were examined at 6 and 12 months post-therapy initiation. Comorbidity was ascertained using modified versions of the RxRisk and RxRisk-V indices and classified as either concordant or discordant with diabetes. Adjusted odds ratios (ORs) and 95% confidence intervals (95%CIs) were determined in relation to comorbidity using logistic regression analysis, adjusting for age, gender and type of OAH prescribed. RESULTS: In the study cohort (n = 21 280), persistence was 74.0% and 62.6% and adherence was 70.0% and 66.7% for all OAHs at 6 and 12 months, respectively. Patients with only concordant comorbidity were significantly more likely to be persistent at 6 (OR 1.45, 95%CI 1.28, 1.65) and 12 months (OR 1.22, 95%CI 1.09, 1.38). Patients with only discordant comorbidity were significantly less likely to be persistent at 6 (OR 0.40, 95%CI 0.35, 0.46) and 12 months (OR 0.43 95%CI 0.38, 0.50) (p < 0.0001). Results were similar for adherence. CONCLUSION: The study suggests that the persistence and adherence of OAH therapy in incident users are affected by the type of comorbidity present; this may help in identifying effective interventions aimed at optimising medication use.