Do Blacks Have Genetic Weakness to Asthma?

SUNDAY Sept. 30, 2007 -- Black Americans who have asthma are much more likely to visit emergency rooms or be hospitalized for the condition than their white counterparts.

That's the finding of a new study that reaches the controversial conclusion that "these findings suggest that genetic differences may underlie these racial disparities."

However, that genetics theory was quickly challenged by some experts in the field.

Previous studies have shown that black people with asthma have worse control of their symptoms and higher rates of hospitalization and death than whites, said the authors of the new study, who noted that adjustments for socioeconomic status have not explained the disparities.

The researchers, from the University of California, San Francisco, studied 678 people -- 524 white and 154 black -- who were being treated for asthma under a large health-care plan and were hospitalized between 2000 and 2004. All were interviewed at the time of hospital discharge about their health status and socioeconomic status, with U.S. Census data used to reinforce their socioeconomic information.

In a follow-up period that averaged 1.9 years, 35.7 percent of the blacks visited emergency rooms for asthma symptoms, compared to 21 percent of the whites. The hospitalization rate was 26.6 percent for the blacks, versus 15.3 percent for the whites.

"Even in a health-care setting that provides uniform access to care, black race was associated with worse asthma outcomes," and genetics could be the difference, said the researchers, who published their findings in the Sept. 24 issue of the Archives of Internal Medicine.

But the reality is not that simple, said Dr. Lauren Smith, an associate professor of pediatrics at Boston University. She led a larger study two years ago that found that socioeconomics played a big role in asthma management when income fell well below the poverty line.

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."

More information

To learn more about asthma, visit the U.S. National Library of Medicine.

Posted: September 2007


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