A new study challenges the widely held belief that inner-city children have a higher risk of asthma simply because of where they live.
Race, ethnicity and income have much stronger effects on asthma risk than where children live, the Johns Hopkins Children's Center researchers reported.
The investigators looked at more than 23,000 children, aged 6 to 17, across the United States and found that asthma rates were 13 percent among inner-city children and 11 percent among those in suburban or rural areas.
But that small difference vanished once other variables were factored in, according to the study published online Jan. 20 in the Journal of Allergy and Clinical Immunology.
Poverty increased the risk of asthma, as did being from certain racial/ethnic groups. Asthma rates were 20 percent for Puerto Ricans, 17 percent for blacks, 10 percent for whites, 9 percent for other Hispanics, and 8 percent for Asians, the study found.
"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," lead investigator Dr. Corrine Keet, a pediatric allergy and asthma specialist, said in a Hopkins news release.
"Instead, we see that poverty and being African American or Puerto Rican are the most potent predictors of asthma risk," Keet added.
The theory that certain features of inner-city life -- including pollution, cockroach and other pest allergens, exposure to indoor smoke, and higher rates of premature birth -- increase children's risk of asthma has existed for about 50 years.
While these factors do boost asthma risk, they may no longer be restricted to inner-city areas. The researchers pointed out that there is increasing poverty in suburban and rural areas, and that racial and ethnic minorities are moving out of inner cities.
"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," study senior author Dr. Elizabeth Matsui, a pediatric asthma specialist and associate professor of pediatrics and epidemiology at Hopkins, said in the news release.