Study finds wider income-based healthcare gaps in the U.S. than in South Korea

Findings from a study published March 20 in JAMA Health Forum showed that higher income is linked to better healthcare access and outcomes in both the U.S. and South Korea, but the gaps are more significant in the U.S. This highlights the need for stronger policies to reduce income-based health inequalities.

Income inequality remains a persistent challenge for health systems and shapes who receives care, the quality of that care and overall health outcomes. The U.S. and South Korea offer a useful comparison because they both face income-related disparities but operate under very different systems, as expressed in the study.

For example, the U.S. relies on a fragmented, market-based model with higher out-of-pocket costs, while South Korea has a universal, single-payer system, though cost barriers still exist. By examining measures such as spending, access, utilization, health status and more, the study took a detailed look at how income influences health system performance in each country.

Researchers from Seoul National University in South Korea, Stanford University and Harvard University, along with the National Bureau of Economic Research, conducted a cross-sectional study using nationally representative survey data from the U.S. and South Korea.

Adults age 18 years or older were grouped into income deciles based on household income. The study looked at 30 measures across six areas, including healthcare spending, utilization, access, health status, behavioral risks and clinical outcomes.

Researchers used regression models adjusted for age, sex and year to estimate income-related differences within each country. They also compared low- and high-income groups and measured disparities across income levels. Additional analyses looked at changes after the Affordable Care Act and differences by age group.

The findings showed wide income-related differences in healthcare spending, use and outcomes in both countries, with larger gaps in the U.S. Income inequality itself was more extreme in the U.S., where households in the top income decile earned about 42 times more than those in the lowest decile compared with a 16-fold gap in South Korea.

Overall healthcare spending was much higher in the U.S., and lower-income adults in both countries spent more on care and relied more on high-cost services such as inpatient and emergency care.

It was found that higher-income adults were more likely to use outpatient and preventive services, with wider gaps seen in the U.S. Patterns of care also differed across systems. For instance, in the U.S., higher-income individuals tended to use more outpatient services, while in South Korea outpatient use declined with higher income. Preventive care use varied as well, with some services more common in the U.S. and others more common in South Korea, though income-related gaps were generally larger in the U.S.

Access to care followed a similar trend.

Higher-income adults in both countries were more likely to report having a usual source of care and fewer unmet medical needs. While there was higher overall use in South Korea, measures of care coordination and consistent access were stronger in the U.S., even among lower-income groups. However, cost-related barriers remained more pronounced among lower-income populations in both countries.

Health outcomes also reflected income differences.

It was also found that self-reported health was better among higher-income adults in both countries, with slightly larger gaps in the U.S. Behavioral risk factors such as smoking, obesity and alcohol use were more common among lower-income groups, again with more pronounced differences in the U.S. Clinical outcomes showed smaller but still present income-related gaps in both countries.

Based on findings, the overall study strengths showed a broad, side-by-side view of health system performance using large, nationally representative datasets and a wide range of measures.

However, the study also had a number of limitations. Study authors shared that it excluded institutionalized adults and relied in part on self-reported data, which could introduce error. Some measures were not fully comparable across countries, and the study could not account for all confounding factors, meaning the findings show associations rather than cause and effect.

In addition, spending estimates didn’t include areas such as long-term care, and the study didn’t capture all possible health outcomes, including quality of care or mortality. The authors also noted that income was measured without accounting for assets, which could underestimate financial resources.

Study authors said the findings point to the need for broader policy solutions, including improving price transparency, strengthening primary care and addressing social and structural factors that drive income-based health disparities.