Long-Term Aspirin Adherence and Risk of Cardiovascular Events and Death After Myocardial Infarction: A Nationwide Cohort Study
Heart attack patients should take aspirin to prevent another heart attack, stroke and death
Heart attack patients who do not take aspirin daily are more likely to suffer a recurrent heart attack, stroke or death compared to those who take the medication consistently, according to research presented at the ESC Congress. 2023.
"Our findings suggest that not taking aspirin as prescribed after a heart attack is linked to an increased risk of having another heart attack, stroke, or death," said study author Dr. Anna Meta Kristensen. from the Bispebjerg and Frederiksberg Hospital. Frederiksberg, Denmark. “We recommend that all patients who have had a heart attack stay true to their aspirin according to the guidelines until randomized controlled trials show otherwise and clinical guidelines have been changed.”
Aspirin is mandatory after a myocardial infarction due to its ability to prevent the formation of blood clots and therefore reduce the risk of a new myocardial infarction or stroke. Because aspirin prevents blood clots, it also increases the risk of bleeding, and the balance between cardiovascular benefits and bleeding changes over time after a cardiac event. This study investigated the risk associated with long-term aspirin discontinuation compared to continued use after a heart attack in a contemporary setting.
The study used data from Danish national health registries. It included patients aged 40 or older who had a heart attack for the first time between 2004 and 2017, were treated with a coronary stent, and took aspirin as prescribed for the first year after the heart attack. Patients who were taking anticoagulants or had a recurrent stroke or heart attack during the first year were excluded.
Adherence to aspirin was assessed at two, four, six, and eight years after the heart attack. In Denmark, every time a patient picks up an aspirin prescription, the number of tablets and the date of collection are recorded in the records. Aspirin adherence at each of the four time points was assessed as the proportion of days patients took their pills during the previous two years.
Patients who took aspirin for 80% or less of the time were considered non-adherent (i.e., they did not take aspirin as prescribed), while those who took aspirin more than 80% of the time were considered adherent (i.e., they took took aspirin as prescribed). At each time point, patients were excluded if they had experienced another heart attack, stroke, died, or started anticoagulants or P2Y12 inhibitors.
Dr. Kristensen explained: “We evaluated the effects of long-term aspirin use in patients who were not receiving other medications for heart attack or stroke prevention. Both anticoagulants and P2Y12 inhibitors are agents that, similar to aspirin, work to prevent the formation of blood clots. Therefore, patients who underwent such treatments were excluded from our study.”
The study included 40,114 patients with a first heart attack. Aspirin adherence decreased progressively with each time point, from 90% at two years after the heart attack to 84% at four years, 82% at six years, and 81% at eight years.
The researchers looked at whether patients who did not take aspirin as prescribed had a higher risk of the composite outcome of recurrent heart attack, stroke, or death compared to those who took aspirin consistently. A number of factors were taken into account that could affect the results, including age, sex, diabetes, high blood pressure, high cholesterol, kidney disease, cancer, stomach ulcers, previous bleeding events, and chronic obstructive pulmonary disease.
At each time point, patients who took aspirin as prescribed were less likely to experience the composite outcome compared to patients who were noncompliant. Compared with adherent patients, nonadherent patients were 29%, 40%, 31%, and 20% more likely to have a recurrent heart attack, stroke, or death at two, four, six, and eight years after heart attack, respectively.
Dr Kristensen said: “Our results should be interpreted with caution because they show an association but do not establish causality. Since the study is registry-based, we do not have information about the specific reasons why patients did not take their aspirin. Additionally, our findings cannot be generalized to all patients who experience a heart attack, as our study focused specifically on those who were treated with a coronary stent and were not taking other medications to prevent blood clots. With that in mind, the results support current guidelines that recommend long-term aspirin after a heart attack.”
Reference: “ Long-term aspirin adherence and risk of cardiovascular events and death after myocardial infarction: A nationwide cohort study .” Anna Meta Dyrvig Kristensen (Bispebjerg and Frederiksberg Hospital - Frederiksberg, Denmark)
