Hispanic heart patients born abroad face a greater risk of dying from cardiovascular disease than their American-born counterparts, according to new research published in the Journal of the American Heart Association.

Hispanics currently make up the largest ethnic minority group in the U.S., first author Fatima Rodriguez, MD, and colleagues wrote in their study, and are projected to grow from a 2014 population of 55 million to 119 million by 2060. In 2014, about a third of all Hispanics living in the U.S. were foreign-born, hailing from South America, Central America, Mexico, the Caribbean and other Spanish-speaking countries.

There also exists an illogical phenomenon in the Hispanic-American population in which Hispanic patients diagnosed with cardiovascular disease (CVD) experience lower age-adjusted CVD mortality rates than non-Hispanic white patients, despite lower levels of income and education and more adverse risk profiles than the latter group, the authors wrote. Clinicians call this the “Hispanic paradox.”

The paradox could be a result of the “healthy immigrant effect,” they explained—the idea that immigration is selective, and only the healthiest, youngest individuals in a population migrate to a host country.

This so-called effect is actually a false stereotype, Rodriguez et al. found. The results of their large-scale study, which analyzed mortality data for 1.3 million Hispanic adults and 18.1 million white adults, actually found foreign-born Hispanic patients had nearly a 17 percent higher CVD and stroke death rate than white patients.

Between foreign- and U.S.-born Hispanics, the researchers found the greatest mortality gap existed in the Cuban population, and the smallest in the Mexican population. Puerto Ricans—classified for the purpose of this study as foreigners, though they’re U.S. citizens—also had higher death rates than those not born on the island.

Puerto Ricans who were born on the U.S. mainland, though, tended to die at a much younger age from CVD: 50 years old versus 73 years old if they’d been born on the island. Cubans saw a similar trend; they were more likely to die from CVD at 63 if born in the U.S. rather than 80 if born in Cuba.

Despite these varying disparities, Rodriguez and colleagues found that whites were overall much more likely to die from CVD than any member of the Hispanic population, regardless of their birthplace.

The authors said their study could be an eye-opener for cardiologists and medical practitioners, who could benefit from being more cognizant of potential communication barriers among native-born Hispanics and raise awareness of their increased CVD risks.

“Our results challenge the commonly held notions of the ‘healthy migrant’ or the ‘salmon bias hypothesis,’" they said. “These theories contend that those who migrate to the United States are healthier and younger than those who chose not to migrate, resulting in a health advantage over the host population.”

Their decade of national mortality data and thorough analyses suggest these theories don’t necessarily translate to reality, they wrote. What they did find, though, has important clinical implications.

“Our findings suggest that public health strategies to improve the cardiovascular health of Hispanic adults in the United States need to consider Hispanic subgroup and nativity status,” they said.