One-year mortality and associated factors in older hospitalized COVID-19 survivors: a Nationwide Cohort Study in Korea

Abstract

This study aimed to evaluate the 1-year mortality rate among older patients with COVID-19 discharged from hospital and to identify risk factors associated with this outcome. Using a COVID-19 dataset from the Korean National Health Insurance System, this study’s evaluation period spanned from October 8, 2020, through December 31, 2021. The primary outcome was the 1-year mortality rate following hospital discharge. A logistic regression model was employed for multivariable analysis to estimate the odds ratios for the outcomes, and the Kaplan-Meier method was used to analyze differences in 1-year survival rates. Among the 66,810 COVID-19 patients aged 60 years or older who were hospitalized during the study period, the in-hospital mortality rate was 4.8% (n = 3219). Among the survivors (n = 63,369), the 1-year mortality rate was 4.9% (n = 3093). Non-survivors, compared to survivors, were significantly older (79.2 ± 9.5 vs. 68.9 ± 7.8, P < 0.001) and exhibited a lower rate of COVID-19 vaccination (63.0% vs. 91.7%, P < 0.001). Additionally, non-survivors experienced a higher incidence of organ dysfunction, along with a greater proportion of required mechanical ventilation (14.6% vs. 1.0%, P < 0.001) and extracorporeal membrane oxygenation (4.0% vs. 0.1%, P < 0.001). Multivariable logistic regression analysis identified older age, male sex, cardiovascular disease, immunosuppression, organ dysfunction, illness severity, and corticosteroid use during hospitalization as factors associated with death within 1 year after hospital discharge. However, vaccination was found to have a long-term protective effect against death among COVID-19 survivors. The 1-year mortality rate after hospital discharge for older COVID-19 patients was comparable to the in-hospital mortality rate for these patients in Korea. The long-term mortality rate among hospitalized older COVID-19 patients was influenced by demographic factors and the severity of illness experienced during hospitalization.