Low Adherence to Statin Treatment during the First Year after an Acute Myocardial Infarction is associated with Increased Second Year Mortality Risk- An Inverse Probability of Treatment Weighted Study on 54,872 Patients

AIMS: Experiencing an acute myocardial infarction (AMI) is a life-threatening event and use of statins can reduce the probability of recurrence and improve long term survival. However, the effectiveness of statins in the real-world setting may be lower than the reported efficacy in randomized clinical trials. Therefore, we aimed to investigate whether low statin treatment adherence during the year following an AMI episode associated with increased second year mortality.

METHODS AND RESULTS: We analysed all 54,872 AMI patients aged ≥45 years, admitted to Swedish hospitals between 2010-2012, and who survive at least one year after the AMI episode. We defined low adherence as a medication possession ratio <50% or non-use of statins. Applying inverse probability of treatment weighting (IPTW) we investigated the association between low adherence and all-cause, cardiovascular (CVD), and non-CVD mortality during the second year.Overall 20% of the patients had low adherence during the first year, and 8% died during the second. In the IPTW analysis, low adherence was associated with an increased risk of all-cause (Absolute risk difference (ARD) =0.048, Number Need to Harm (NNH) =21, Relative Risk (RR) =1.71), CVD (ARD=0.035, NNH=29, RR = 1.62) and non-CVD mortality (ARD=0.013, NNH=77, RR = 2.17).

CONCLUSION: In the real-world setting, low statin adherence during the first year after an AMI episode is associated with increased mortality during the second year. Our results reaffirm the importance of achieving a high adherence to statin treatment after suffering from an AMI.