It’s fairly established medical science that people who have had heart attacks can take regular low doses of aspirin to significantly lower their risk of having another heart attack, or other heart problems including stroke. But it is still an open question whether or not people who haven’t had a heart event, but are at higher risk of one (because, for example) they have diabetes, high blood pressure, or elevated cholesterol levels), can also benefit from the over-the-counter painkiller and anti-inflammatory drug.

A new study, published in the Journal of the American Heart Association, adds to that debate by addressing a gap in the research on the subject: whether race or ethnicity makes a difference in how aspirin affects their risk of heart disease.

The U.S. Preventive Services Task Force (USPSTF), an independent body of experts convened by the U.S. government to explore such health questions, determined in 2016 that people could prevent a first heart attack by taking low-dose aspirin if they are between 50 to 59 years old and have a greater than 10% risk of a heart event in the next 10 years. (That overall risk is calculated by taking into account a variety of risk factors such as weight, blood pressure, cholesterol and diabetes.)

But for those between 60 and 69 years old, the USPSTF recommends discussing the benefits and risks with a doctor; while aspirin can lower the inflammation that pushes plaques in the blood vessels to rupture and then form clots that can cause heart attacks, it can also lead to bleeding in the gastrointestinal tract. Because of this risk, some experts have been backing away from advising older people who have not yet had any heart events from taking daily aspirin.

In the recent study, Dr. Rodrigo Fernandez-Jiminez, a researcher at the Spanish National Center for Cardiovascular Research, and his team analyzed data from the Southern Community Cohort Study, which included more than 62,000 people from 12 states in the southeastern U.S. The participants answered questions about their lifestyle behaviors, including exercise and diet, and the researchers collected information on the subjects’ medical profile, including their medication use and heart disease risk factors. What set the cohort apart was the fact that most of the participants came from lower socioeconomic backgrounds, making it a relatively homogeneous population when it came to access to health care and insurance. About two-thirds of the volunteers identified as African-American or non-Hispanic black.

That allowed Fernandez-Jiminez and his team to explore race’s potential role in aspirin’s ability to prevent first heart events, something previous research hasn’t adequately addressed. “Most trials that have happened so far do not include different racial and ethnic groups,” he says. “And African-Americans are totally under-represented in these studies, so the guidelines have no conclusions about the potential differential effect aspirin could have on different racial groups. We didn’t have any hypotheses going into the study because this was almost the first data analyzing this issue.”

Despite identifying with a range of ethnic backgrounds, the study participants were similar socioeconomically, which means that factor wasn’t likely to explain differences the researchers found: After a median follow up of 11 years, the scientists learned that for people reporting taking low-dose aspirin, the risk of dying from a heart event increased by 18% among those identifying as black, while in participants identifying as non-Hispanic white, that risk declined by 14%.

However, it’s important to note that this doesn’t mean categorically that aspirin isn’t effective in this population. Income-related factors, such as access to health care and medications, aren’t likely to play a role, since this study controlled for those, but there may be other social factors at play. There could, for example, be differences in how faithfully people in a given population take a daily pill like aspirin, as well as what other medications they might be taking that could interfere with aspirin’s beneficial effects on the heart. In the study’s highest-risk group, for example, 18% of black participants reported being on a low-dose aspirin regime, compared to 27% of white participants. Genetic factors may also contribute to how people from different racial and ethnic backgrounds biologically respond to drugs like aspirin.

Fernandez-Jiminez says the current study was not designed to tease out what might be causing the difference in aspirin’s effect on heart deaths among those identifying as black vs. those identifying as white. But documenting the disparity is the first step toward understanding it better. “Our work is not enough to make specific recommendations or change guidelines,” he says. “But it points to the need for more information in general about the differential effect drugs can have on different racial or ethnic groups.”

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