Public Release: 

Race Plus Roaches: A Breathtaking Link

Johns Hopkins Medicine

African-Americans are far more likely than Caucasians to develop asthma linked to cockroach sensitivity, according to research from the Johns Hopkins Children's Center.

In a recent study of more than 80 Baltimore youth, the researchers found that an African-American child was 16.4 times more likely than a Caucasian child to be sensitive to allergens left behind by cockroach droppings and saliva. And poor children or those from out of cities were 11.9 times more likely to be affected by roach infestation than those from middle or high income families.

The study in the June issue of The Journal of Allergy and Clinical Immunology is also the first to report that children in the most infested homes are the most sensitive to the allergens, a clear indication of dose responsiveness, the researchers say.

"We honestly don't know why race plays a role independent of poverty," says Peyton Eggleston, M.D., professor of pediatrics and co-author of the study. Eggleston speculates that racially based genetic differences, important in the regulation of immune responses, hold a clue.

Low socioeconomic status forces families to live in substandard housing, whether urban or suburban, he says. Older homes, or those in crowded areas, give cockroaches a fertile breeding ground.

The domestic cockroach has been identified as a source of indoor allergen worldwide, both in temperate and tropical climates. Although more than 60 species have been identified, the most common in North America are the German, Oriental, and American cockroaches.

Cockroach allergens are known to represent an important risk factor for acute asthma, a condition that causes the bronchi of the lungs to constrict. Onset almost always occurs in childhood. Serious illness and even death can result. For example, in Baltimore City, where the study was conducted, asthma is the number one cause of absenteeism from school, says Eggleston. And recent epidemiologic data show that African-Americans living in the inner-city are hospitalized three times as often and die five times more often from asthma than those of other races.

The study included 66 boys and 21 girls, 48 Caucasian and 39 African-American children from 37 urban and 50 suburban homes. All had moderate to severe allergic asthma.

The researchers hunted for evidence of two different cockroach allergens, called Bla g1 and Bla g2, in the floors, bedding and stuffed furniture of homes. The allergen samples were collected using a handheld vacuum cleaner equipped with individual collection bags.

Detectable levels of cockroach allergen were found in 26 percent of urban and suburban bedrooms, where children spend the most number of consecutive hours. Over 80 percent of the children with cockroach residue in their bedrooms were allergic to the allergens.

Other risk factors, such as age, gender and place of residence, were studied. But none proved as significant as race and family income level.

According to Eggleston, the researchers hope to use this information to perform further studies that better their understanding of the root causes of cockroach allergen.

The study was funded by the National Institute of Allergy and Infectious Disease (NIAID). Other researchers include Sampson B. Sarpong, M.D., Robert G. Hamilton, Ph.D., and N. Franklin Adkinson, Jr., M.D.


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