Comparison of health care utilisation and spending among National Health Insurance and Medical Aid beneficiaries in Korea

Understanding the effect of out-of-pocket expenses on health service use is important for the financial sustainability of health care systems. This study compared health service use and spending between National Health Insurance (NHI) and Medical Aid (MA) beneficiaries in Korea. We conducted a retrospective ecological study with a repeated cross-sectional design using nationwide health insurance claims data covering the NHI and MA beneficiaries in Korea from 2011 to 2023. We examined the demographic composition of the two groups and their health care utilisation by age. We compared per capita spending between the NHI and MA beneficiaries for common diagnoses. Lastly, we assessed changes in per capita health care spending and utilisation between the two groups over the study period by estimating average annual percent change. In 2023, inpatient spending among MA beneficiaries (USD 3,011) was more than five times as high as that of NHI beneficiaries (USD 576), and the average length of stay among MA beneficiaries was 87.9 days, about 4.8 times that of NHI beneficiaries (18.4 days). The gap was most pronounced among male MA beneficiaries aged 30–49, with inpatient spending 13 to 14 times that of the NHI group and length of stay showing a similarly large difference. Outpatient and pharmacy spending and utilisation were also more than twice as high among MA beneficiaries. Elevated spending among MA beneficiaries was especially evident for musculoskeletal conditions and chronic mental health conditions. While both groups showed significant increases in spending and utilisation from 2011 to 2023, MA beneficiaries consistently had higher per capita spending (MA to NHI ratio, 3.3–3.6), with a fivefold gap in inpatient care. The substantial gap in health care utilisation between NHI and MA beneficiaries highlights the need to investigate potential overuse. Developing strategies to limit unnecessary health service use while maintaining access is a crucial issue for ensuring a sustainable health care system.