NEW YORK CITY—Racial differences in sensitivity to the indoor allergens that worsen asthma exist throughout the United States, a study has demonstrated for the first time.[1] In a nationally representative sample of 4,164 children ages 6 to 16 years, African-Americans and Mexican-Americans were significantly more likely than white Americans to be sensitive to cockroach and dust mite allergens; African-American children were also at higher risk of Alternaria alternata sensitivity.

“Alternaria in particular has been associated with death from asthma,” lead study author Lori A. Stevenson, MPH, told RESPIRATORY REVIEWS. Ms. Stevenson is an investigator in the Center for Urban Epidemiologic Studies at the New York Academy of Medicine in New York City.

The study findings are consistent with, and may help explain, the disproportionate asthma morbidity and mortality that exists among African-Americans and other disadvantaged populations. The observed racial differences in allergen sensitivity were independent of other socioeconomic factors, Ms. Stevenson added.

SKIN TESTS DETERMINED SENSITIVITY

The children in the study had previously undergone skin testing for allergies during the Third National Health and Nutrition Examination Survey (NHANES III), conducted from 1988 to 1994 to assess the health of the noninstitutionalized US civilian population.[2] Skin tests were performed for sensitivity to cockroach, dust mite, cat, and A alternata allergens, as well as to positive and negative controls (histamine phosphate and 50% glycerol saline).

To ensure adequate sample sizes, Ms. Stevenson and colleagues restricted their analysis of the relationship between sociodemographics and allergen sensitivity to African-American, Mexican-American, and white children. Those with missing, incomplete, or invalid skin test results were excluded. So were those with missing information for key sociodemographics—race, age, sex, education, household income, family history of atopy and allergy, region of residence, age of the home they occupied, and the amount of crowding.

Because residence in a central city was determined only during the first four years of NHANES III, such information was available for only 2,149 children. This population was included in a secondary analysis of the link between urban residence and allergen sensitivity.

INFLUENCE OF RACE

Overall, 43% of the children were sensitive to at least one of the allergens studied. About 20% were sensitive to cockroach, 25% to dust mite, and roughly 15% each to cat or A alternata.

Multivariate analysis showed that race was significantly and independently correlated with sensitivity to all of the allergens except cat allergen. The odds ratios (ORs) for cockroach, dust mite, and A alternata sensitivity in African-American children (compared with that in white children) were 2.5, 1.3, and 2.1, respectively. Mexican-American children displayed increased sensitivity only to cockroach and dust mite allergens, with ORs (again, in comparison to white children) of 1.9 and 1.6, respectively.

The likelihood of cat sensitivity was twice as high in older children (those ages 12 to 16 years) as it was in younger ones. Older age, a family history of atopy or allergy, and male sex were each independently associated with sensitivity to all of the allergens studied.

Geography appeared to affect only the odds of dust mite sensitivity: Children living in the western United States were less likely than children living elsewhere to be sensitive to this allergen.

In the secondary analyses, racial differences in allergen sensitivity were greatest in the central city. Crowding (defined as living in a home with more than 1.5 persons per room) more than doubled the odds of cockroach sensitivity, the analyses also showed.

IS HOUSING THE CULPRIT?

These findings raise the question: Is housing responsible for the greater allergen sensitivity among minority children? Many data support that hypothesis. The 1997 American Housing Survey, for example, found that African-Americans were more likely than whites to report living in multiple-dwelling residences, having water leaks or evidence of rodents in their home, and being exposed to other housing characteristics known to promote indoor allergen proliferation.

Available evidence supports the development and adoption of public health and housing policies to reduce allergen exposure among all children, stressed Ms. Stevenson. “Such policies might be especially important in minority communities, where it seems that the burden of allergen sensitivity is particularly large,” she concluded.

—Timothy Begany