Disparities in avoidable hospitalization by income in South Korea: data from the National Health Insurance cohort

Background: Avoidable hospitalizations can act as an indicator for primary health care quality, in particular ambulatory care sensitive conditions (ACSCs) as hospitalizations for these conditions are generally considered avoidable through successful management. This study aimed to examine whether differences exist between income levels in rates of avoidable hospitalization. Methods: The South Korea National Health Insurance claims data from 2002 to 2013 were used. All hospitalizations were included and categorized into avoidable and non-avoidable cases. The independent variable was income level classified into quartiles and the dependent variable rates of avoidable hospitalization. Analysis was conducted using the generalized estimating equation (GEE) Poisson model. Subgroup analysis was performed based on chronic versus acute disease status and urban versus rural region. Results: A total of 1 310 492 cases were included, in which the crude rate of avoidable hospitalizations was 1444.5 per 100 000 person years. Compared to the Q4 highest income group set as reference, the Q3 (RR 1.07, 95% CI 1.04-1.09), Q2 (RR 1.16, 95% CI 1.13-1.19) and Q1 (RR 1.20, 95% CI 1.17-1.24) income groups showed higher rates of avoidable hospitalizations. Conclusion: Risks of avoidable hospitalizations for ACSCs was higher in lower than higher income groups, implying that socioeconomic status is related to disparities in avoidable hospitalizations. The findings suggest the importance of monitoring the vulnerable groups identified in managing avoidable hospitalizations.