More than 50 years ago, public health experts suggested the environmental and experiential factors common to urban areas — including pollution, cockroach and other pest allergens, and higher rates of premature births — meant inner-city children are more likely to develop asthma than their suburban or rural counterparts. Since these conditions are no longer exclusive to inner-city areas, Johns Hopkins researchers decided to examine this possibly out-of-date belief. Asthma risk among children living in urban areas is not higher, their new study concludes; income, race, and ethnic origin are more likely to influence asthma risk than physical surroundings.

"Our findings suggest that focusing on inner cities as the epicenters of asthma may lead physicians and public health experts to overlook newly emerging 'hot zones' with high asthma rates," Dr. Elizabeth Matsui, senior author and associate professor at the Johns Hopkins University School of Medicine, stated in a press release.

With poverty rising in suburban and rural areas — and ethnic and racial minorities moving out of the inner city — Matsui and her co-authors suggest it’s time public health efforts reflect the new demographics. What, then, are the exact numbers of kids diagnosed with asthma?

Based on a survey of 23,065 children between the ages of 6 and 17, the Johns Hopkins study finds 12.9 percent of inner-city children have asthma compared with 10.6 percent of children living elsewhere. Once the researchers factored variables such as race, ethnicity, and geographic region into their analysis, though, this difference vanished like smoke in the air.

Income, Genetics, Place

Family poverty had a stronger influence on a child’s asthma risk than overall neighborhood poverty. Children of families with incomes below the national poverty threshold were more likely to be diagnosed with asthma and have an asthma attack requiring emergency treatment than the children of families with higher incomes. As annual income went down, the risk of having an emergency asthma episode or a diagnosis of asthma both crept up.

While personal poverty drives asthma risk, the study also revealed differences based on ethnicity and race. Asthma rates among Puerto Rican and African-American children — 20 percent and 17 percent, respectively — outpaced rates among other groups: eight percent for Asians, nine percent for other Hispanics, and 10 percent for whites. In fact, being African-American or Puerto Rican is a substantial risk factor even after eliminating the influence of other variables, including household income and geographic area. To explain this discrepancy, the researchers note that the increase risk among these two groups is well-known among scientists and due to biologic and genetic differences.

Finally, the study revealed inner-city asthma rates vary widely by region. The Northeast showed the highest rates (17 percent of inner city kids diagnosed), while the West had the lowest rates (eight percent). Some poor suburban and rural areas showed higher asthma rates than those found in the inner city. Low-income suburban areas of the Northeast, for instance, reached 21 percent asthma prevalence among children compared with 17 percent in the corresponding urban area. The same was true in the Midwest; there, low-income areas in medium metro areas showed 26 percent asthma prevalence compared with 15 percent in corresponding urban areas.

Source: Keet CA, McCormack MC, Pollack CE, et al. Neighborhood poverty, urban residence, race/ethnicity, and asthma: Rethinking the inner-city asthma epidemic. Journal of Allergy and Clinical Immunology. 2015.