Recurrence and Mortality Risks in Patients with First Incident Acute Stroke or Myocardial Infarction: A Longitudinal Study Using the Korean National Health Insurance Service Database

Background: We aimed to identify the long-term risk of recurrence and mortality in patients who experienced acute ischemic stroke (AIS), acute myocardial infarction (AMI), or acute hemorrhagic stroke (AHS) using a population-level database. Methods: This retrospective cohort study included adults aged ≥55 years diagnosed with AIS, AMI, and AHS in the National Health Insurance Service Database between 2004 and 2007. The target outcomes were secondary AIS, AMI, AHS, and all-cause mortality. Predetermined covariates, such as age, sex, socioeconomic status, hypertension, diabetes, and dyslipidemia, were adjusted. Results: We included 151,181, 49,077, and 41,636 patients in the AIS, AHS, and AMI groups, respectively. The AMI (adjusted hazard ratio [aHR], 0.318; 95% confidence interval [CI], 0.306–0.330; p < 0.001) and AHS (aHR, 0.489; 95% CI, 0.472–0.506; p < 0.001) groups had a significantly lower risk of developing secondary AIS than the AIS group. The risk of developing secondary AMI was significantly lower in the AMI (aHR, 0.388; 95% CI, 0.348–0.433; p < 0.001) and AHS (aHR, 0.711; 95% CI, 0.640–0.790; p < 0.001) groups than in the AIS group. Initial AHS was a decisive risk factor for secondary AHS (aHR, 8.546; 95% CI, 8.218–8.887; p < 0.001). The AMI (aHR, 1.436; 95% CI, 1.412–1.461; p < 0.001) and AHS (aHR, 1.328; 95% CI, 1.309–1.348; p < 0.001) groups were associated with a significantly higher risk of long-term mortality than the AIS group. Conclusion: Our results elucidated that initial AIS was a significant risk factor for recurrent AIS and AMI; initial AHS was a decisive risk factor for developing secondary AHS. Further, AMI and AHS were more closely related to long-term mortality than AIS.