Why do so many black kids have asthma?

If policymakers want to tackle the most common chronic condition among children, they’ll have to tackle inequality first.

That's the takeaway from a pair of studies out of Rice University analyzing how neighborhood-level disadvantage affects asthma diagnosis in Houston.

"We know some of the physiological components of asthma," explained Justin Denney, co-author on both studies and director of the Urban Health Program, part of Rice University's Kinder Institute for Urban Research. "But it's also complicated from a social [and] economic exposure to environment perspective. That adds this whole other layer of complexity."

Even as childhood asthma rates appear to be flat nationally — or maybe even declining — large disparities still exist. Nationally, 13 percent of black children have asthma compared to 7 percent of white children, according to the Centers of Disease Control and Prevention. People living in poverty also more likely to be diagnosed with asthma.

Similar disparities exist in the Houston area, according to the new studies, which were supported by Houston Endowment.

Researchers found, for example, that children in the Houston area with public insurance, often used as a proxy for low socioeconomic status, were 21 percent more likely to have asthma than children with private insurance. Meanwhile, 4 percent of white and Asian children here had asthma diagnoses, compared to 13 percent of black and 7 percent of Hispanic children.

"Houston is particularly interesting for our question because we're really interested in the racial disparities observed in asthma and bringing in the neighborhood environment," said Mackenzie Brewer, co-author on one of the new papers that examines asthma diagnoses.* "It's a pretty unique opportunity in Houston, just because of the diversity we have."

In one study co-authored by Brewer and five others, researchers looked at the zip codes of children diagnosed with asthma to determine whether neighborhood disadvantage — a combination of poverty, unemployment, the percentage of households receiving public assistance and the percentage of female-headed households with children — and the racial composition or relative segregation of a neighborhood, were tied to higher asthma rates. They also looked at neighborhood pollution, with two different measures of air quality.

They found children living in economically and socially disadvantaged neighborhoods tended to have higher asthma rates. However, researchers also suggested there were likely other factors at play as well that were not specifically captured in their measures but likely related to them: things like exposure to violence or crime, safety concerns and other health-damaging chronic sources of stress.

"Aspects of neighborhood environment certainly did matter," explained Brewer. "That said, the disparity was still very high – black children were still over twice as likely to receive a diagnosis than white children — after we [controlled for] those neighborhood factors."

In a separate study,** working with similar data, researchers went a step further, categorizing zip codes into three distinct neighborhoods types — advantaged, middle class and disadvantaged — using even more neighborhood-level data, including median income and the median age of houses. But the results here were similarly complicated. So while neighborhood differences mattered, they didn't explain as much as was expected, said Ashley Kranjac, co-author of that study.

Across the three neighborhood types, Kranjac and the other researchers found, that "African American children, compared to white children, experienced a higher probability of asthma diagnosis...but the more disadvantaged the neighborhood, the larger the difference."

But Kranjac said that trend may also be related to systemic disadvantage. Without more robust individual-level data from the hospital records, she said, individual inputs, like whether a house has central heating, how often a kid is able to leave his or her neighborhood for extracurricular activities and whether air quality at a child's school is better than at home, it's difficult to account for those potential disadvantages as well.

"While those racial disparities are still pretty stark," said Kranjac, "we do show that neighborhoods matter. We have to have continued and sustained efforts to understand how the neighborhoods kids are living in will affect their life outcomes."

Both studies point to the fact that "there are disparities because of the social economic inequalities in society," added Denney. "If we deal with educational disparities, if we deal with poverty, if we deal with those issues, we're actually dealing with health issues," he explained. "We think these underlying issues are fundamental drivers of the problem."

* "Does neighborhood social and environmental context impact race/ethnic disparities in childhood asthma?" Mackenzie Brewer, Rachel Tolbert Kimbro, Justin T. Denney, Kristin M. Osiecki, Brady Moffett, Keila Lopez.

** "Comprehensive Neighborhood Portraits and Child Asthma Disparities" Ashley W. Kranjac, Rachel T. Kimbro, Justin T. Denney, Kristin M. Osiecki, Brady S. Moffett, Keila N. Lopez.

Leah Binkovitz (@leahbink), formerly of the Houston Chronicle, is now a staff writer for Rice University's Kinder Institute. This story originally appeared on the Kinder Institute's blog, The Urban Edge.

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