Key Points:

• African-Americans may be more susceptible to the harmful effects of tobacco, and thus more likely to develop COPD, than white Americans are. • Among children with moderate to severe asthma, those of Puerto Rican or African-American descent are more likely to be sensitized to a number of indoor and outdoor allergens; asthma management may improve if these allergens are identified.

PHILADELPHIA—New research is uncovering evidence that ethnicity may influence the development of chronic obstructive pulmonary disease (COPD) and asthma. One recent study, for example, found that among patients with advanced COPD, the African-Americans had equally severe disease as did the white Americans, even though they were younger, had started smoking later in life, and had smoked less.[1] This finding is at odds with the prevailing view that COPD tends to be more severe in whites.

“Our data may reflect a genuine biological difference in the effect of smoking on African-Americans and whites, or they could be artifactual,” acknowledged lead author Wissam M. Chatila, MD. “More research will be needed to confirm our findings,” said Dr. Chatila, an Associate Professor of Pulmonary and Critical Care Medicine at Temple University in Philadelphia.

Another recent study identified differences between ethnic groups in the risk of allergen sensitization. Among children with mild to severe asthma, those of either Puerto Rican or African-American descent had a higher rate of sensitization than did the white children.[2] While the Puerto Rican and African-American children were more likely to be sensitized to certain indoor allergens (such as dust mites and cockroaches) than were the white children, they were also more likely to be sensitized to outdoor allergens.

The higher rates of sensitization among Puerto Rican and African-American children are probably due, at least in part, to their greater likelihood of living in poor housing conditions, suggested Juan C. Celedón, MD, an Assistant Professor of Medicine at Harvard Medical School in Boston. However, the finding has important implications for management. “Not knowing that an asthmatic child is sensitive to certain allergens … can ultimately make asthma treatment more difficult,” he emphasized.

RACE, SEX, AND COPD

In an interview, Dr. Chatila said that he is certain his study pertains to COPD and that it is highly unlikely that undetected asthma could have influenced the results. “We retrospectively identified patients who were evaluated for lung volume reduction or lung transplantation—procedures used to treat COPD but never asthma,” he explained.

Also, in his study, COPD had been diagnosed and staged according to the GOLD (Global Initiative for Chronic Obstructive Lung Disease) criteria. Thus, the 80 African-American and 80 white patients all had key traits of severe COPD, including a smoking history of 15 or more pack-years and an FEV1 below 50% of predicted without significant bronchodilator response.

At presentation, the two groups had similarly poor lung function and performed equally on cardiopulmonary exercise tests. On average, however, the African-American patients were four years younger than the white patients (58 vs 62), had a shorter smoking history (44 vs 66 pack-years), and had begun smoking at a later age (18 vs 16).

A gender analysis yielded similar findings. The women were younger than the men, had smoked less, and had started smoking later in life. Furthermore, although cardiopulmonary exercise and lung function test results were comparable between the sexes, the women were more hypercapnic.

When the results were analyzed by both race and sex, some surprises emerged. For example, the African-American women tended to present with COPD at an even earlier age than did white women (56 vs 60), noted Dr. Chatila. White men had by far the heaviest smoking histories.

He admits that these findings are preliminary. “We need to be careful when interpreting the results of the study,” Dr. Chatila cautioned, “because there is still the possibility of selection bias.” Nevertheless, previous research provides evidence that a difference between the races in COPD onset is biologically plausible. For example, African-Americans tend to have smaller lung volumes than white patients do, and they might have different inflammatory responses based on differences in risk factors.

It is Dr. Chatila’s hope that his study will help to make African-Americans more aware of their risk for severe obstructive lung disease and to change physicians’ perception that COPD is a disease of whites. “We also hope to develop a smoking intervention targeted specifically to African-Americans because they have been less successful in their attempts to quit smoking compared to whites,” he added.

ETHNICITY AND ASTHMA

Dr. Celedón’s study included 791 children with mild to severe asthma who received their medical care in Hartford, Connecticut. All had been referred for allergy skin testing. About 44% of the children were white, 39% were Puerto Rican, 14% were African-American, and 3% were from other ethnic groups.

In comparison to the white children, the Puerto Rican and African-American children were more likely to live in an urban area and to be participants in the Medicaid program. In addition, they were more likely to have eczema or severe persistent asthma and to be exposed frequently to rodents, cockroaches, or both at home.

Using multivariate analysis to control for these variables, Dr. Celedón and his colleagues found that Puerto Rican children were three times as likely as white children were to be sensitized to cockroaches and almost twice as likely to be sensitized to dust mites. The African-American children also had a marked increase in the risk of cockroach sensitization in comparison to white children, but the difference did not quite reach statistical significance. In contrast, white children were twice as likely to be sensitized to dogs as the Puerto Rican and African-American children were.

Differences in sensitization to outdoor allergens were also observed. In comparison to the white children, the Puerto Rican children were more likely to be sensitized to mixed grass pollen, mugwort/sage, and weed mix; the African-American children had higher rates of sensitization to mixed tree pollen, mixed grass pollen, ragweed, and mugwort/sage.

In the overall study population, sensitivity to a particular allergen often strongly predicted which children would have four or more positive skin test results. For example, the odds ratio for such an outcome was 50.6 among those who were sensitive to mugwort/sage, 32.4 among those with ragweed sensitivity, and 9.9 among dust mite–sensitized children.

Despite the use of multivariate analysis, the study authors could not completely eliminate the possibility that socioeconomic differences among the groups contributed to the varying rates of sensitization. However, it is probable that unidentified genetic and environmental factors, and not increased exposure to indoor allergens, explain the Puerto Rican children’s increased susceptibility to dust mites, Dr. Celedón noted, because Puerto Rican ethnicity has been associated with relatively low levels of dust mite in the homes of children with asthma. Unidentified genetic and environmental factors may also be partially responsible for the increased sensitization levels found in the African-American children.

Until these factors are identified, the best approach may be more widespread use of allergy testing. “Physicians managing asthma in Puerto Rican or African-American children may find allergy skin testing helpful, particularly when the asthma is severe or hard to treat,” Dr. Celedón concluded.

—Timothy Begany

References
1. Chatila WM, Wynkoop WA, Vance G, Criner GJ. Smoking patterns in African Americans and whites with advanced COPD. Chest. 2004;125:15-21.
2. Celedón JC, Sredl D, Weiss ST, et al. Ethnicity and skin test reactivity to aeroallergens among asthmatic children in Connecticut. Chest. 2004;125:85-92.

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