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UBC Theses and Dissertations

Persistence and adherence with cardiovascular and lipid-lowering drugs following acute myocardial infarction in British Columbia Pataky, Reka Elizabeth


BACKGROUND – Pharmaceutical use for the secondary prevention of cardiac events after acute myocardial infarction (AMI) is widespread, but there is uncertainty as to how (or if) patients use their medicines over long periods of time. Accordingly, the purpose of this thesis is 1) to measure persistence with and adherence to ACE inhibitors, beta blockers and statins, following AMI in BC, 2) to construct a conceptually-driven model of adherence and persistence, with patient demographic, socioeconomic, health status and pharmaceutical use variables, and 3) to determine whether regional variation in adherence and persistence rates exist. METHODS – Using administrative data from the BC Linked Health Database and PharmaNet, I studied a cohort of BC patients who were hospitalized for their first AMI between 2001 and 2005. I measured persistence as days to first 90-day gap in medication, and I measured adherence in two ways: the proportion of days covered (PDC) between first prescription and first 90-day gap, and PDC in the first year post-discharge (1-year PDC). Rates of persistence and adherence were analyzed using Cox proportional hazards models and multivariate logistic regression respectively. RESULTS – Patient persistence and adherence with medication was generally high, with 70% of ACE inhibitor users, 73% of beta blocker users and 78% of statin users persisting at one year. Nearly 89% of users of any class were persistent at 1 year, as opposed to 52% of users of all three concurrently. Factors consistently associated with high adherence and persistence were high income, private insurance, the use of more drug classes (both before and after AMI), and being in the mid-range of age (60-69 years). Sex had mixed effects between classes, with women having higher persistence and adherence with beta blockers and lower with ACE inhibitors. Some regional variation existed, but effects were small and inconsistent. CONCLUSION – Most AMI patients in BC use at least one drug for several years after AMI, but few persist with all three recommended classes. Important next steps include determining the clinical outcomes of adherence and persistence, especially with drug combinations, to more clearly define optimal secondary prevention practices following AMI.

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