Results of a new study by Johns Hopkins researchers using national data add to evidence that living in inner cities can worsen asthma in poor children. They also document persistent racial/ethnic disparities in asthma.

A report of the study’s findings, published in The Journal of Allergy and Clinical Immunology on March 8, shows that urban living and black race are strong independent risk factors for increased asthma morbidity – defined as higher rates of asthma–related emergency room visits and hospitalizations – but urban living does not increase the risk for having asthma.

“Our findings serve as evidence that there are differences between risk factors linked to developing asthma and those linked to making asthma worse if you already have it,” says Corinne Keet, MD, PhD, associate professor of pediatrics at the Johns Hopkins University School of Medicine and the paper’s lead author.

The research team sought to determine those effects by analyzing information gathered by the U.S. Centers for Medicare and Medicaid Services on the health care utilization of 16,860,716 children ages 5 to 19 who were enrolled in Medicaid in 2009 and 2010.

The team first narrowed the pool of data to children who had at least one asthma–related outpatient or Emergency Department visit over the two–year period. Based on the county they lived in, these 1,534,820 children were categorized by urbanization status and based on their ZIP code, categorized as living in a poor or not poor neighborhood.

The results for 18 states that met the study’s final guidelines showed that children who lived in nonurban areas were 18 to 21 percent less likely to be at risk for hospitalizations, even after accounting for race/ethnicity. The researchers also found that compared to non–Hispanic white children, black children and children of “other” races had 89 and 61 percent, respectively, higher risks of asthma–related hospitalizations.

Unlike other racial/ethnic groups, Hispanic children who live in a nonurban area did not experience reduced risks of emergency room visits or hospitalizations. And contrary to Keet’s previous studies, which reported that poverty was protective against asthma prevalence rates for Hispanic children, the team found no similar association for asthma morbidity.

Keet says that among the Medicaid population she studied, 30 percent of asthma–related hospitalizations were likely attributable to socioeconomic, geographic and/or racial/ethnic disparities; 19 percent of hospitalizations were estimated to be attributable to black race/ethnicity; 4 percent were attributable to living in a poor area; and 7 percent were attributable to living in an urban area.

Children who lived in inner–city areas had an overall 40 percent higher risk of asthma–related emergency room visits and 62 percent higher risk of asthma–related hospitalizations. After adjusting for race/ethnicity, risk was lowered to 14 percent and 30 percent higher for emergency room visits and hospitalizations, respectively.

“These results show that despite several decades of research on racial/ethnic and geographic disparities in asthma morbidity, there are still very large differences in rates of emergency room visits and hospitalizations by race and neighborhood characteristics. These findings emphasize that we need to redouble our efforts to find comprehensive solutions to address asthma disparities,” concludes Keet.