Methods: Children in 8 urban centres in the United States who experienced either hospitalization due to asthma or at least two unexpected clinic or emergency room visits due to asthma were recruited to participate in this randomized control trial. All children lived in a US census tract where 20% of the population lived below the US federal poverty line. All children received clinical testing to determine sensitivity to various allergens and a home environment assessment session at the start of the study. The children were randomly assigned to either a comparison group or an intervention group. The intervention group received focused in-person education sessions on dust mites, passive smoking, cockroaches, pets, rodents and mold along with follow-up telephone calls. During the intervention year, the intervention group also received a median of 5 in-person visits. In addition, allergen-impermeable covers were placed on mattresses, high efficiency particulate air (HEPA) filters were set up in each child's bedroom and the families were given vacuums with HEPA filters. Both the comparison and the intervention groups received follow-up home assessments every 6 months. The clinical symptoms of all children were assessed through bimonthly telephone calls and through 2 spirometry tests (a laboratory test designed to measure expiratory flow rate). Study follow-up continued for two years after enrollment.

Findings: A total of 937 children, with an average age of 7.7 years, were enrolled in the study. The intervention group experienced 0.82 fewer symptom days in a two-week period in year 1 and 0.60 fewer days in year 2. Furthermore, the number of caregiver and child nights of sleep lost due to asthma and the number of school days missed was lower in the intervention group. The intervention group also experienced fewer unscheduled visits to a clinic or emergency department in year 1, but this difference was not significant in year 2. The levels of dust mite and cat allergens in the child's bed and the levels of cockroach, dust mite and cat allergens on the bedroom floor were lower in the intervention group in Year 1 compared to the comparison group. In Year 2, this difference continued to be observed for dust mite and cat allergens in the child's bed. The lower levels of asthma symptoms seen in the intervention group were related to the reduction in allergen levels. The intervention was estimated to cost between $1,500 US and $2,000 US per child for all personnel visits and equipment.

Conclusions: This study shows that interventions that reduce home-based allergens can be effective in reducing the morbidity associated with asthma in urban children. The program may have been successful because it targeted multiple exposures rather than focusing on only one allergen. A formal economic evaluation still needs to be conducted so that policy makers may understand the financial implications of these types of interventions.

Reference: Morgan, WJ, Crain, EF, Gruchalla, RS, and others. "Results of a Home-Based Environmental Intervention Among Urban Children with Asthma." New England Journal of Medicine 2004; 351: 1068 - 1080.

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