Association between readmission and mortality in patients with ischemic stroke: evidence from national health insurance service database of South Korea

Background The association between hospital readmission after ischemic stroke (IS) and long-term mortality remains insufficiently understood. This study examined the relationship between 90-day readmission and all-cause mortality over a 3-year follow-up period among patients experiencing their first IS. Methods This retrospective cohort study used claims data from the National Health Insurance Service (NHIS) of South Korea. Patients discharged after hospitalization for IS between 2019 and 2020 were followed for 90 days to ascertain readmission status. Three readmission models were constructed based on clinical breadth: Model 1 (IS recurrence), Model 2 (IS and related diseases), and Model 3 (all-cause readmission). Propensity score–matched cohorts were analyzed using Kaplan–Meier methods and multivariable Cox proportional hazards models to assess associations with subsequent 3-year mortality. Results Among 22,548 patients included in the analysis, 83.3% (18,790) survived and 16.7% (3,758) died during the 3-year follow-up period. Kaplan–Meier analyses demonstrated significantly lower survival probabilities among patients readmitted within 90 days compared with those not readmitted across all three models (log-rank p < 0.05). In multivariable analyses, 90-day readmission was consistently associated with higher 3-year mortality (adjusted hazard ratio [aHR] range: 1.15–1.38). Higher mortality risk was observed among male patients (aHR ≈ 1.7), adults aged ≥ 80 years (aHR ≈ 5.3), and underweight individuals with body mass index < 18.5 kg/m² (aHR ≈ 2.0). In contrast, engagement in light physical activity and moderate-to-vigorous exercise was associated with lower mortality risk (aHR ≈ 0.74–0.78). Conclusion Hospital readmission within 90 days after ischemic stroke was consistently associated with increased long-term mortality. In this observational study, early readmission may serve as a marker of clinical vulnerability, and the findings support the potential value of structured, stroke-specific transitional care models aimed at reducing avoidable readmissions. Implementing tailored transitional care interventions at discharge may help identify high-risk patients early and support continuity of care, thereby potentially mitigating adverse long-term outcomes after ischemic stroke.