Long-Term Risk of Acute Myocardial Infarction in Patients With a Transient Ischemic Attack: A Danish Nationwide Cohort Study

BACKGROUND: Sparse information regarding the long-term risk of acute myocardial infarction (MI) following a transient ischemic attack (TIA) emphasizes further research to guide preventive strategies and risk stratification in patients with a TIA. METHODS: We conducted a nationwide cohort study to investigate the 5-year risk of MI and all-cause mortality in patients with a first-time TIA. Patients with a first-time TIA were identified in the Danish Stroke Registry (2013–2020), matched on age, sex, and calendar year (1:4) with the general population and (1:1) with patients with first-time ischemic stroke. The 5-year risks of MI and all-cause mortality were estimated by the Aalen-Johansen and Kaplan-Meier estimators. The groups were compared using Cox regression, while adjusting for cardiovascular comorbidities. RESULTS: We identified 21 743 patients with TIA, 86 972 matched individuals from the general population, and 21 743 matched control patients with ischemic stroke. Median age was 70 (25th to 75th percentile, 60–78) years; 52% were male. Comorbidity burden was the lowest in general population controls, intermediate in patients with TIA, and the highest in patients with ischemic stroke. The 5-year risk of MI was 2.0% in patients with TIA, 1.5% in the general population ( P <0.001), and 2.2% in the ischemic stroke population ( P <0.001). After adjustment, these differences in MI rate were similar (TIA versus general population; hazard ratio, 0.99 [95% CI, 0.98–1.02] and TIA versus ischemic stroke; hazard ratio, 0.99 [95% CI, 0.96–1.01]). The 5-year risk of mortality was 17.0% in patients with TIA compared with 14.0% in the general population ( P <0.001) and 27.0% in ischemic stroke population ( P <0.001). The differences in mortality persisted following adjustments for patients with TIA versus general population (hazard ratio, 1.25 [95% CI, 1.19–1.31]) and for patients with TIA versus ischemic stroke (hazard ratio, 0.43 [95% CI, 0.41–0.46]). CONCLUSIONS: Patients with first-time TIA had a low 5-year incidence of MI, which was not significantly different from that of the general population and patients with first-time ischemic stroke after adjustments for comorbidities. However, patients with TIA had a 25% higher all-cause mortality rate than the general population, which was not readily explained by MI risk. Hence, the findings do not endorse the need to raise further awareness regarding MI in patients with TIA.