Kate Johnson

February 25, 2013

SAN ANTONIO, Texas — Home-based interventions to reduce cockroach-related asthma are most effective in violent neighborhoods where children spend more time indoors, according to a study presented here at the American Academy of Allergy, Asthma & Immunology 2013 Annual Meeting.

"Increased exposure to cockroach allergen can certainly exacerbate asthma in children who are sensitized," lead researcher Michelle Sever, PhD, from the University of North Carolina at Chapel Hill, told Medscape Medical News.

She and her colleagues found that children who live in violent neighborhoods had more than 12 asthma symptom days in a 2-week period. "The children who were sensitized to cockroach allergen and had the highest violence exposure actually received the greatest benefit from the reduced cockroach allergen intervention. The children not exposed to violence still benefited, but not as much," Dr. Sever reported.

A previous study showed that exposure to community violence predicts a higher baseline number of asthma symptom days in children (P = .0008) (Am J Public Health. 2004;94:625-632).

Dr. Sever and colleagues used data from the Inner City Asthma Study (N Engl J Med. 2004;9;351:1068-1080), which involved 937 children 5 to 11 years of age from 7 sites in the United States. The children lived in census tracts in which at least 20% of the homes were below the poverty level.

All children had doctor-diagnosed asthma and 1 asthma-related hospitalization or 2 unscheduled clinic or emergency department visits in the 6 months prior to enrollment. They also had at least 1 positive allergy skin test, and 60% were allergic to cockroach allergen, Dr. Sever said.

The researchers collected dust samples every 6 months during the 2-year study period to investigate the interaction between indoor allergen exposure, sensitization, asthma, and community violence.

They used a questionnaire to score exposure to community violence, skin prick tests to measure allergen sensitization, and dust sample assays from each child's bedroom to measure exposure. The cutoff they used to define exposure was 2 units/g.

At baseline, asthma symptom days increased in association with higher community violence, but only in children who had been both exposed and sensitized to cockroach allergen (P for interaction = .07).

Reducing Allergens

Among those who were sensitized, an intervention that resulted in a 1 log-unit decrease in allergen exposure was associated with decreased symptoms (P for interaction = .2).

"Asthma symptoms went down across the board, but the interesting thing is the trend that shows the children who are sensitized to cockroach allergen and exposed to violence have the greatest reduction in asthma following decreased allergen exposure," Dr. Sever explained.

These findings support the hypothesis "that higher asthma morbidity in children who are exposed to violence...is due at least in part to spending more time indoors and the resultant higher exposure to cockroach allergen," she said. Efforts to decrease home cockroach allergen exposure will likely be a more feasible intervention than decreasing violence, she noted.

However, she acknowledged, other asthma triggers could also be at play.

Other Triggers

"We could not measure any markers of stress in these children, so that pathway remains open to investigation," Dr. Sever pointed out. "I call it a very murky pool we work in with asthma and the inner city.... Unfortunately, we don't have information about exposure to stress or exposure to domestic violence."

"There's not much published in this area; it's an interesting issue," said Jonathan Bernstein, MD, from the University of Cincinnati in Ohio, who is editor-in-chief of the Journal of Asthma. He was asked by Medscape Medical News to comment on the study.

He explained that mental health and psychosocial triggers are important factors to consider, especially in the context of urban violence.

"It's a little more complex than just being indoors.... Depression and anxiety are heavily associated with asthma. When we talk about treatment, we target it toward inhaled steroids and long-acting beta-agonists. [However], if you just do that, you're never going to control it, because it's also about managing the environment at home and at the workplace or school, and dealing with the interactions between parent and child, physician and patient, and all the psychosocial issues," he explained.

This study was funded by the National Institutes of Health. Dr. Sever and Dr. Bernstein have disclosed no relevant financial relationships.

American Academy of Allergy, Asthma & Immunology (AAAAI) 2013 Annual Meeting: Abstract 200. Presented February 23, 2013.