The San Francisco researchers said they adjusted for socioeconomic factors, "but even when one looks at such factors, there are differences that often go unincorporated because they are not easy to handle," Smith said. "Housing quality, segregation in the neighborhood, these are things that generally are not accounted for when you control for socioeconomic status. And the experience of race is complicated, and the measures you have to look at socioeconomic status generally are broad."
Those factors mean that "a genetic explanation needs to pass a high bar to come to that conclusion," Smith said.
The worse outcome for blacks could be partially explained by another factor noted in the study, Smith said, that blacks were less likely to achieve control of their asthma with medications. "There are substantial differences in medication use, and that is an important thing to recognize as a possible contributor," she said.
Dr. Ronina Covar, a staff physician at the National Jewish Medical and Research Center in Denver, said the strength of the new study is that it eliminates one confounding factor from previous studies. "In this case, they all had equal health care," she said.
But "they obviously don't present any genetic data," Covar said. Still, she said, genetics "could be one of the mechanisms and possible explanations for the findings."
To learn more about asthma, visit the U.S. National Library of Medicine.
SOURCES: Lauren Smith, M.D., associate professor, pediatrics, Boston University; Ronina Covar, M.D., staff physician, National Jewish Medical and Research Center, Denver; Sept. 24, 2007, Archives of Internal Medicine
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