Time to rethink the inner-city asthma epidemic?

Challenging the long-standing belief that city dwellers suffer disproportionately from asthma, the results of a new Johns Hopkins Children's Center study of more than 23,000 U.S. children reveal that income, race and ethnic origin may play far more potent roles in asthma risk than kids' physical surroundings.

The study, based on comparison of childhood asthma rates in cities and outside of them, found no differences in asthma risk between children living in urban areas and their suburban and rural counterparts.

The findings, published online Jan. 20 in the Journal of Allergy and Clinical Immunology, showed a surprisingly uneven distribution of asthma - one that fails to follow traditional patterns of urban and nonurban residence, the team says. Significantly, the investigators say, they found a powerful link between poverty and African-American race and Puerto Rican ethnicity and a higher-than-average asthma risk.

"Our results highlight the changing face of pediatric asthma and suggest that living in an urban area is, by itself, not a risk factor for asthma," says lead investigator Corinne Keet, M.D., Ph.D., a pediatric allergy and asthma specialist at Johns Hopkins.

"Instead, we see that poverty and being African American or Puerto Rican are the most potent predictors of asthma risk."

The idea that certain aspects of urban living - pollution, cockroach and other pest allergens, higher rates of premature births, exposure to indoor smoke - make inner-city children more prone to developing asthma emerged more than 50 years ago, when public health experts first described an epidemic of inner-city asthma cases. While all those factors continue to fuel asthma risk, the investigators say, they may no longer be exclusive to or even predominant in inner-city areas, and the new study findings bear out this phenomenon.

The results, the researchers say, reflect powerful demographic shifts at work, such as increasing poverty in suburban and rural areas, and the movement of racial and ethnic minorities out of inner cities. Therefore, they add, public health interventions should also reflect this changing reality.

"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," says senior author Elizabeth Matsui, M.D., M.H.S., pediatric asthma specialist and associate professor of pediatrics and epidemiology at the Johns Hopkins University School of Medicine.

The investigators caution that their research focused solely on baseline asthma risk - in other words, whether a child living in the city is more likely to have asthma than a child living in the suburbs or in the country. Their present study, they add, was not designed to capture whether inner-city children who have asthma suffer worse symptoms or require more medical attention than children with asthma who live elsewhere. The latter question, the researchers say, is the subject of a separate investigation already under way.