Are higher rates of asthma among Blacks and Hispanics due to genetics or environment? Yes.

Published on
September 27, 2022

Nick, a 13-year-old Latino who lives in town of Turlock in California’s Central Valley, has been rushed to the emergency room twice in his life, at ages 4 and 6, because of an asthma attack. His lung muscles were having such severe spasms that air couldn’t get in. His lips were turning blue. His blood oxygen dropped to 87%, with normal being at least 94%. 

“He couldn’t stop coughing, couldn’t catch his breath and it was horrifying,” said Patty Guerra, Nick’s mother.

What Nick remembers most is that the doctors in urgent care put him in the ambulance slated for a patient having a heart attack for transit to the local hospital. That patient was stable, but Nick was not. 

“It just feels like you’re trying to breathe through a straw,” he said.

The teen is one of 4 million U.S. kids with asthma, which disproportionately impacts Black and Latino families, as well those lower on the income scale. And as recent research reveals, neighborhoods matter quite a bit too, but an individual’s ZIP code doesn’t fully explain asthma’s well-documented racial disparities. 

Nick’s mother said that he later improved with breathing treatments, and he hasn’t had a severe attack in years. His asthma is under control with medications, and he knows the triggers for an attack, which include pollen, environmental allergies and heat. These are all frequent threats, since he is growing up in California’s Central Valley, with its abundant crops and scorching temperatures. 

Nick has some attributes thought to protect him against asthma though. He lives in a more affluent census tract and his parents are college educated, often used by researchers as a marker for higher socioeconomic status. 

On the other hand, Nick is Hispanic, which may increase his susceptibility for asthma, according to a recent report in JAMA Pediatrics

For the study, researchers compared neighborhood-level economic factors with wheezing and asthma prevalence in more than 5,000 children under 18 in a nationwide trial. Neighborhoods were defined by census tracts, which are small areas with an average population of 4,000 people, used by the U.S. Census Bureau for statistical analyses. 

They found that children of all races and ethnicities who lived in tracts with more low-income households, higher population density and more poverty had increased rates of asthma.

In addition, Black and Hispanic-origin children had higher rates of asthma and asthma-related complications than whites, regardless of their census tract or mother’s education. The researchers didn’t differentiate children with Hispanic ancestry into groups such as Spanish, Puerto Rican or Mexican, among others.

In other words, poverty and neighborhood characteristics are linked to higher asthma rates, but they don’t fully explain the racial disparities. Something else is going on as well, but researchers haven’t yet arrived at a complete explanation. 

The study’s finding that poverty as a risk factor for asthma fits with national data reported by the Centers for Disease Control and Prevention. Poverty doesn’t affect everyone equally: In the U.S., Blacks and Hispanic-origin groups are overrepresented among those living in poverty.

Globally, an estimated 300 million people have asthma, with nearly a half million deaths annually. Asthma prevalence is higher in more affluent countries, but asthma symptoms tend to be more severe in lower-income countries.

In the U.S., more than 4 million kids 18 and younger suffer with asthma, making it the most common chronic disease of childhood. Asthma prevalence is higher among Black, non-Mexican Hispanic especially Puerto Ricans and Indigenous kids, than among white and Asian children. Asthma rates are even higher for Black and Latino children in urban areas. However, asthma attacks among all children have declined since the peaks in the 1980s and ’90s.

These research findings beg the question of what role genetics, race and ethnicity play compared to poverty and environment when it comes to asthma disparities.

“I think it’s genetics and gene-environment interactions,” said Dr. Esteban Burchard, asthma researcher, epidemiologist and a distinguished professor of medicine at the University of California, San Francisco. 

Risk factors for developing asthma are complex and interrelated, and they begin before birth. Children born to parents with asthma are three to six times more likely to develop asthma than children born to parents without asthma. Exposure to smoke in the womb increases a baby’s risk, as does being born prematurely or having a respiratory virus infection during infancy or early childhood. 

Living in an unhealthy environment, including exposure to pollutants, substandard housing, poor diet and less access to health care, is a significant contributor to asthma risk. 

Burchard said his interest in the interactions between genes and the environment in respiratory diseases was spurred in part by two studies in the 1990s. One study reported higher rates of asthma among Puerto Ricans, compared to Dominicans or other Latinos living in the same building in a housing project in New York City. The other investigation found higher asthma deaths for Hispanics in the Northeast, where Puerto Rican ancestry is more common, as compare to the South and West, where Mexican and Central American ancestry is more common.

“Something is coming through the Puerto Rican gene pool that’s causing the higher prevalence of asthma,” Burchard said. 

He has also investigated the higher rates of asthma among African Americans, including the effects of systemic racism. In addition, Blacks on average take longer to clear the body of some pollutants, such as nicotine, which may contribute to the risks for asthma, lung cancer, obesity and heart disease. 

“Being Black makes health outcomes worse. I think it’s racism internalized, maybe it’s epigenetics,” said Burchard. Epigenetics refers to how behaviors and the environment can affect how genes are expressed, without changing the underlying DNA.

Burchard has written about the detrimental effects of racism in medical care upon the health of minorities. For example, Black and Hispanic children were less likely to receive asthma-controlling medications or patient education and were more likely to be diagnosed with asthma than white children with similar symptoms in a military health system with universal coverage. 

In another survey, Black and Latino parents were less likely to trust the health care system and reported feeling discriminated upon by providers, which made them hesitant to seek care. 

Nick identifies as Mexican American, and despite his higher socioeconomic status, parents with no asthma history, and ready access to medical care, he has asthma. The impact of his environment is less clear, but it does include some of the known triggers for an attack.

Burchard said unlocking some of the remaining questions on the role played by ancestry and genetic clues is essential for eliminating asthma disparities. But that will first require better diversity in clinical trials. He noted less than 5% of genetic studies of respiratory diseases include non-whites.

“I want to make sure that minority communities raise their hands to be included in research. It may not benefit them, but it will benefit subsequent generations.”