Aspirin nonadherence after MI increases long-term risk for recurrent MI, stroke, death
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Key takeaways:
- Aspirin nonadherence became more prevalent over time, from 10% at 2 years to 19% at 8 years.
- The greatest risk for recurrent MI, stroke or death occurred at 2 to 4 years for the adherent and nonadherent groups.
People who did not adhere to a long-term aspirin regimen after an MI had a higher risk for recurrent MI, stroke or death, although the risk appeared less pronounced among older adults and women, according to study results.
“Aspirin has an undisputed role in the acute phase of MI, but the paradigm that all patients should be treated lifelong with aspirin therapy in secondary prevention of cardiovascular disease has been questioned,” Anna Meta Dyrvig Kristensen, MD, of the department of cardiology at Copenhagen University Hospital – Bispebjerg and Frederiksberg, Denmark, and colleagues wrote in European Heart Journal – Quality of Care and Clinical Outcomes. “Early trials of aspirin after MI were all of relatively short duration, with 1 to 4 years of post-MI follow-up.”
The analysis included 40,116 participants aged 40 years and older (74% men; mean age, 63.8 years) who had an MI from 2004 to 2017 and took aspirin for at least 1 year after. Researchers followed up with patients at 2, 4, 6 and 8 years after MI to track aspirin adherence using data from the Danish National Prescription Registry. Participants who were covered for more than 80% of days at each time point were considered adherent, whereas researchers considered those with 80% or less coverage as nonadherent.
A composite of recurrent MI, ischemic stroke or all-cause mortality served as the study’s primary outcome.
Researchers noted that the number of participants decreased at each time point, from 37,591 at 2 years to 14,491 at 8 years.
Nonadherence rose from 10% of participants at 2 years to 19% at 8 years.
Researchers found that adherent participants tended to be older and had a greater burden of hypertension and diabetes, whereas nonadherent participants had slightly higher education levels. Socioeconomic status appeared similar across both groups.
The standardized absolute risk for recurrent MI, stroke or death was highest at 2 to 4 years after initial MI. The risk for the adherent group was 8.34% (95% CI, 8.05-8.64), and the risk for the nonadherent group was 10.72% (95% CI, 9.78-11.66).
The standardized RR for the primary outcome decreased over time, from 1.41 (95% CI, 1.27-1.55) at 4 to 6 years and 1.31 (95% CI, 1.17-1.46) at 6 to 8 years to 1.21 (95% CI, 1.06-1.36) at 8 to 10 years.
This trend did not persist across all age groups. Nonadherence among participants older than 65 years did not carry a higher risk for the primary outcome than adherence. However, among participants aged 65 years and younger, those who were nonadherent had significantly higher risk at every time point except at 8 to 10 years.
Sex also played a role. At 4 to 6 years and 6 to 8 years, the risk for the primary outcome was not significantly higher among nonadherent women, although it remained higher among nonadherent men.
“Further studies are needed and should be directed at investigating whether long-term aspirin is beneficial in specific populations, such as older women,” the researchers wrote. “The diminished efficacy observed in the older population might be attributed to age-related changes in platelet function and decreased responsiveness to aspirin. Future studies should aim to explore platelet reactivity in older individuals to further elucidate this aspect.”
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Kristensen AMD, et al. Eur Heart J Qual Care Clin Outcomes. 2024;doi:10.1093/ehjqcco/qcae009.
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