Income-based disparities in the care and outcomes experienced by patients with acute myocardial infarction (MI) are seen around the world, despite vastly different healthcare and social safety net systems, a new study shows.

Researchers analyzed data on patients with acute MI from six different high-income countries and found rates of appropriate treatment were lower and mortality rates were generally higher in low-income individuals compared with high-income individuals, despite vastly different healthcare systems.

“The feeling has been that the US does worse in terms of healthcare disparities than countries with more integrated holistic healthcare systems, but our results found that low-income individuals did worse across the board even in countries like the UK or Canada that have a national insurance system,” lead author Bruce Landon, MD, MBA, Department of Health Care Policy, Harvard Medical School, Boston, told theheart.org | Medscape Cardiology.

“So, while the US isn’t doing well in this regard, other countries aren’t either. This suggests that health systems across the world need to redouble their efforts to try to improve the provision of equitable care across the whole spectrum of the population,” he added. 

The study was published online April 4 in the Journal of the American Medical Association.

The authors explain that many international comparisons, reliant on aggregated country-level data, have reported that the US spends more but has poorer health. But these analyses lack detailed information on how disease-specific processes of care and outcomes differ for patients presenting with a single illness or condition across different countries.

Such information could provide insights into the potential impact of health system factors on treatment and outcomes for specific conditions as distinct from other social factors, which consistently have been shown to be major factors influencing health.

They developed the International Health System Research Collaborative (IHSRC) to facilitate population-level comparisons of treatment patterns and outcomes in the US, Canada, England, the Netherlands, Israel, and Taiwan, countries with highly developed healthcare systems and accessible administrative data but that have significant differences in financing, organization, and performance in international rankings.

For the current study, the researchers compared differences in acute MI treatment (eg, cardiac catheterization, revascularization) and outcomes (mortality, readmissions) for high- and low-income patients across the six countries.

They point out that acute MI is a suitable condition for cross-country comparison because it is common, has internationally agreed-upon diagnostic criteria, and has validated coding schemes in administrative data. In addition, patients with acute MI are consistently hospitalized in high-income countries, so hospital data generally capture all cases.

They analyzed administrative claims data to identify all adults aged 66 years or older hospitalized for at least 1 day (or who died on the day of admission) with a primary diagnosis of ST-elevation MI (STEMI) or non-STEMI between 2013 and 2018 in the 6 IHSRC countries (Canada was represented by data from the provinces of Ontario and Manitoba). A total of 289,376 hospitalizations for STEMI and 843,046 for NSTEMI were included.

Patients with an acute MI admission during the year prior were excluded to avoid counting readmissions as new admissions. Data on demographic information (age, sex) and comorbidities was recorded.

In most countries, high-income patients were defined as those living in a postal code in the top 20% of the income distribution and low-income as those living in areas in the bottom 20% of the distribution. In the Netherlands, household income was observed for individuals, rather than areas.

Results showed that adjusted 30-day and 1-year mortality for both STEMI and NSTEMI were lower for the high-income patients in all countries except Taiwan.

The largest differences in 30-day mortality were seen in Canada for STEMI (14.9% vs 17.8% for high vs low) and Israel for NSTEMI (8.8% vs 11.5%).

One-year mortality differences were larger, with the highest difference being in Israel (16.2% vs 25.3% for STEMI and 22.2% vs 28.9% for NSTEMI).

The US data showed similar pattern with 30-day mortality rates of 18.4% for the highest socioeconomic status-quintile vs 20.2% for the lowest socioeconomic status-quintile in STEMI patients, and 11.6% vs 12.3% for non-STEMI patients. 

One-year mortality rates were 27% vs 29.8% for high-income vs low-income US STEMI patients, and 28.3% vs 30.2% for those with non-STEMI.

Other results showed that 30-day readmission rates were consistently lower for higher-income patients for both STEMI and NSTEMI, and that rates of cardiac catheterization and percutaneous coronary intervention within 90 days of admission for STEMI (the most appropriate treatment) were higher for high-income patients than for low-income patients in all countries.

“Our study challenges an important and deeply held belief that income-based disparities in health and healthcare are larger in the US than other high-income countries, although with the caveat that an older population that is eligible for Medicare coverage was examined, which may be more similar to available coverage in other countries,” the authors conclude.

Landon commented: “There has long been a narrative that the US healthcare system is more expensive and has worse outcomes than other countries. We have been frustrated that while people often look at the outcomes of the healthcare system, a lot of these are actually secondary to other issues in society as opposed to what the healthcare system actually does. In this study we really tried to isolate the impact of factors specific to the healthcare system on outcomes.

“We find that high-income individuals get more appropriate treatment and have better outcomes regardless of where they live,” he added. “While we do not do a good job in treating disadvantaged people compared to advantaged people in the US, it turns out we are not an outlier. This is challenge throughout the world. That doesn’t mean it is no less important. We all need to work on improving our outcomes for disadvantaged people.”

Landon believes the results reflect a combination of factors affecting disadvantaged individuals, including worse healthcare but also less access to exercise, good nutrition, and other kinds of preventive care.

“In this study we are isolating individuals at the same timepoint of presentation of disease, so we think most of what we are finding is related to how people are being treated in the system. But there may also be some factors that we can’t measure that cause disadvantaged patients to be sicker.”

While acknowledging that higher-income individuals are probably better accessing care, Landon added: “We need to think about that in the design of our systems to facilitate similar access for people who don’t have quite the same wherewithal to access care themselves.”

The study was supported by the US National Institute on Aging and by ICES, which is funded by an annual grant from the Ontario Ministry of Health and the Ministry of Long-Term Care. Conflict of interest disclosures can be found with the original article.

JAMA. Published online April 4, 2023. Abstract 

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