The deep divide between the health of black and white Americans has a long and painful history, drawing the attention of scholars from W.E.B. Du Bois in the late 19th century to public health researchers today who track seemingly intractable differences in health, medical treatment, life expectancy, and death.

Du Bois was not surprised that impoverished people suffered ill health and inferior treatment as a byproduct of discrimination; more than a hundred years later, a growing body of evidence has documented continuing disparities in the health of African-Americans compared with their white counterparts.

A new study examining how long black or white people survive after a heart attack concludes that it’s socioeconomic status, far more than race, that explains who fares better.

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Previous studies have focused on black patients being less likely than white patients to receive the standard of care both before and after having a heart attack, placing them at higher risk for another heart attack, another hospitalization, and death. Some of those disparities in care and outcomes have narrowed, but inequalities persist between how ill black and white patients are after a heart attack and how many die.

Other research has hinted that the race of a patient may be only a reflection of socioeconomic and health status, coming before any differences in treatment, and the new study, published Friday in JAMA Network Open, found that all of the difference in outcomes was accounted for by socioeconomic factors.

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The stress of racial discrimination has been shown to increase blood pressure, a risk for heart attack. Living in a poor neighborhood can limit opportunities for exercise or good nutrition, both of which raise the odds of obesity and heart disease. Low income can mean making choices between paying the rent or paying for medication to control diabetes, another condition that predisposes people to cardiovascular disease.

Dr. Garth Graham and his colleagues set out to understand these and other factors associated with racial differences in heart attack survival, analyzing the exposures and experiences of white and black patients to determine which ones are linked to different outcomes.

Looking at 6,402 patients who were treated at 31 hospitals across the country, researchers found a persistent gap in death rates five years after a heart attack: 29 percent of black people had died versus 18 percent of white people, outcomes in line with previous studies reflecting the outsized impact of heart disease on minority populations. But looking more closely at certain socioeconomic factors — living in a lower-income ZIP code, having less education, being unemployed — the researchers found an even wider gap. People living with more of those socioeconomic factors were three times more likely to die in the five years after a heart attack than people with fewer of those factors.

Those characteristics are more prevalent in the African-American population, Graham and his colleagues say. But accounting for those characteristics erased the racial differences in outcomes, leading the researchers to conclude that race is only a proxy for factors disproportionately affecting black people, highlighting the need to eliminate socioeconomic disparities.

“We need to look more at what’s happening upstream and before they get to the hospital,” Graham said in an interview. “To eliminate health disparities, this opens up where we may best target our efforts.”

In their analysis, the researchers assigned scores to a variety of socioeconomic and medical factors. Low income and its cluster of related factors were tied most strongly to higher mortality, even more so than poor medical status, for both black and white patients. And they found that the way patients were treated in the hospital did not differ significantly by their race or income, ruling that out as a factor in patients’ survival.

“These outcomes, although they seemed linked to race, were actually independent of race in and of itself,” said Graham, a cardiologist at Saint Luke’s Mid America Heart Institute and the University of Missouri-Kansas City School of Medicine. “For patients who have a set of characteristics that are more prevalent in the African-American communities, that may result in a threefold difference in mortality, whether they are black or white.”

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Dr. Herman Taylor, director of the Cardiovascular Research Institute at the Morehouse School of Medicine, called the study provocative and statistically rigorous. He leads the Jackson Heart Study, the largest epidemiological study of African-Americans and cardiovascular disease, and has studied the health consequences of social adversity.

“That’s a powerful statement to say that if you take all these factors into account, they don’t have anything inherently to do with your biological state or with your ethnicity, that being of African-American descent is not the issue so much as what that means in the American context,” Taylor said. “All Americans should enjoy the same levels of health. It shouldn’t be that you see substantially different mortality rates from heart disease in one ZIP code versus another.”

Dr. Ashish Jha, director of the Harvard Global Health Institute at the Harvard T.H. Chan School of Public Health, cautioned that the takeaway is not that race and racism don’t matter to people’s health.

“I think saying race was just a proxy diminishes the power of race and I would argue this study helps us better understand how race influences these things, but I don’t think it somehow negates the importance of race,” Jha said. “I think it’s very hard in our country to say racism is not important. This paper teaches us about the mechanisms by which race affects health outcomes.”