Socioeconomic and Regional Disparities in Long-Term Mortality among Intensive Care Unit Survivors in South Korea: Nationwide Cohort Study.

Background:Long-term outcomes of intensive care unit (ICU) survivors remain a major public health concern. Despite the existence of a universal health care system in South Korea, socioeconomic and regional disparities may affect postcritical illness survival. Objective:In this nationwide cohort study, we aimed to examine the associations of socioeconomic and regional factors with long-term mortality among ICU survivors. Methods:We conducted a retrospective population-based cohort study using data from the Korean National Health Insurance Service (NHIS). We included adult patients (≥20 y) admitted to ICUs between 2015 and 2019 who survived to hospital discharge. Patients admitted for injury-related or external causes were excluded. Postdischarge socioeconomic status (SES) indicators included insurance type (National Health Insurance [NHI] vs Medical Aid [MA]), NHIS eligibility status, and income level quartiles. Residential area was analyzed separately as a regional contextual factor. The primary outcome was all-cause mortality for up to 8 years after discharge, which was estimated using the Kaplan-Meier method. Adjusted hazard ratios (aHRs) and 95% CIs were estimated using multivariable time-dependent Cox proportional hazards models stratified by age (20-39 y, 40-64 y, and ≥65 y). Results:Among 871,366 adult ICU survivors, 9.6% (n=83,766) were MA beneficiaries. Lower SES-defined by MA coverage, nonemployee NHIS eligibility categories, and lower income level-was consistently associated with higher long-term mortality. Compared with NHI enrollees, MA recipients had an aHR of 1.63 (95% CI 1.60-1.66) among middle-aged adults and 1.48 (95% CI 1.38-1.60) among younger adults. Dependents and self-employed insured household members had 2-fold to 3-fold higher mortality risk than employee-insured beneficiaries. A stepwise income-mortality gradient was evident across all age groups. Residence in other regions was also associated with higher mortality (aHR 1.06-1.11). Younger individuals were particularly vulnerable to SES-related disparities. Conclusions:Despite South Korea's universal insurance system, socioeconomic and regional disparities in long-term mortality persist among ICU survivors. Ensuring equitable access to post-ICU care, income security, and targeted social support may help promote sustainable recovery.