Patients with suboptimal adherence to guideline-recommended medications following myocardial infarction (MI) have increased risk of adverse outcomes.
To determine the association between adherence to statins, beta blockers (BB), renin-angiotensin aldosterone system inhibitors (RAASi) and clopidogrel in the year following MI and cardiovascular outcomes using restricted cubic spline (RCS) analysis.
We identified a cohort of 5938 patients aged >65 years in Western Australia who had an MI from 2003-2008 and survived one-year post-discharge. Adherence was calculated using proportion of days covered (PDC) from first medication supply date to one-year post-discharge (landmark date). Outcomes were major adverse cardiac events (MACE) and death within one-year following the landmark date. Cox proportional hazard models with RCSs were used to determine associations between PDC adherence (linear or categorical) and outcomes.
A 10% decrease in adherence to statins in the landmark period significantly increased the one-year risk of MACE (5.1%) and death (6.2%). BB adherence did not affect either outcome at any level of adherence. RAASi and clopidogrel showed curvilinear RCS relationships. Lower levels of adherence to RAASi (<70% and 70-<90% versus ≥90%) significantly increased the risk of death (33.2% and 28.2% respectively). Adherence <90% to clopidogrel significantly increased the risk of death by approximately 30%.
In seniors who survived one-year post-MI, higher adherence to statins was associated with lower risk of MACE and death. In contrast, BB had no effect, whilst high adherence to RAASi and clopidogrel is important. RCSs are useful for visualising the relationship between adherence and outcomes.