Income‐Level and Immigrant Status Are Associated With Discontinuation of Evidence‐Based Secondary Prevention Therapies After Myocardial Infarction

BACKGROUND: Mechanisms for worse prognosis after myocardial infarction in low socioeconomic status are unclear. We therefore investigated the association between socioeconomic status and discontinuation of evidence-based secondary prevention drug therapies. METHODS: All patients with a first-ever myocardial infarction, on treatment with a statin (n=60 717), antithrombotic therapy (n=65 862), or a renin-angiotensin-aldosterone-system inhibitor (n=51 486) at the routine 1-year visit in SWEDEHEART (Swedish Web-System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies) between January 2006 and mid-2020 were included in this population-based nationwide cohort study. Individual-level socioeconomic status was measured by disposable income quintile, region of birth, and educational level. Outcomes were discontinuation (>180 days without a new prescription claim) of statins, antithrombotic therapies, and renin-angiotensin-aldosterone-system-inhibitors. Bias-minimized multivariable adjusted hazard ratios (aHRs) were estimated during follow-up until December 2020. RESULTS: Discontinuation occurred more often in the lowest versus highest income quintile for statins (aHR, 1.25 [95% CI, 1.20-1.31]), antithrombotic therapy (aHR, 1.26 [95% CI, 1.20-1.32]), and renin-angiotensin-aldosterone-system inhibitors (aHR, 1.32 [95% CI, 1.26-1.39]). Discontinuation of statins was more frequent among immigrants (versus nonimmigrants) born in other Nordic (aHR, 1.24 [95% CI, 1.17-1.32]), other European (aHR, 1.40 [95% CI, 1.33-1.47]), Asian (aHR, 1.45 [95% CI, 1.36-1.56]), and other world regions (aHR, 1.63 [95% CI, 1.45-1.84]). Associations between immigrant background and discontinuation of antithrombotic therapies and renin-angiotensin-aldosterone-system inhibitors were even stronger. Lower (versus tertiary) educational level was inversely associated with discontinuation of secondary prevention drug classes. CONCLUSIONS: Despite Swedish universal health care, discontinuation of evidence-based drugs post myocardial infarction is strongly associated with disposable income and immigrant background. Further study on strategies to improve adherence in low socioeconomic status post myocardial infarction is warranted.