Is Indoor Home Intervention for Asthma Effective?

Elizabeth Matsui, MD, MHS

The success of environmental interventions in the home for asthma have been met with skepticism and uncertainty from experts, mainly due to conflicting clinical trial results.

In a survey of American Academy of Allergy, Asthma, and Immunology (AAAAI) members, 75% reported emphasizing the importance of environmental control, and 66% reported providing educational material to do so. While the majority appears to believe there is some success with these remediations, it is hard to ignore the other 25%.

At the 2018 AAAAI/World Allergy Organization (WAO) Joint Congress in Orlando, Florida, Elizabeth Matsui, MD, MHS, a professor of pediatrics at Johns Hopkins Medicine, explained that the way allergists approach these data need to shift, as interpretations of trial data have been a root cause of some of the cynicism about these interventions.

“How do we make sense of conflicting trial results?” Matsui said. “We need standardized reporting framework. Interventions may have clinical effects through pathways other than allergen reduction, so interventions should be interpreted in the context of this step.”

The current method of inferring data has been to observe if intervening lowers the allergen and if the lowered allergen thus improves asthma, Matsui said, but she noted that it is important to recognize that intervening may improve asthma without impacting the allergen.

To make her case, Matsui pointed to 6 studies with disagreeing results—3 positive, 3 negative&mdash;for mouse, cockroach, mite, and composite allergens. The trio of positive trials, all conducted with children, resulted in 2 most allergen exposure changes (<50%) and 1 large change (>50%). The negative trials, 1 with children, 1 with adults, and 1 with a mixture of both, showed no difference, a large (>50%) but not sustained change, and a small to nonexistent change, respectively.

This lack of agreement has led to current guidelines to ignore environmental intervention in regard to recommended action against asthma.

“The Global Initiative for Asthma does not recommend allergen avoidance as a general strategy for asthma,” Matsui said. “The National Asthma Education and Prevention Program does, however, give a nod to [environmental interventions]. It suggests reducing, if possible, exposure to allergens to which the patient is sensitized and exposed.”

Other recommendations from the Global Initiative for Asthma suggest that there is no evidence of clinical benefits for asthma with single-strategy indoor allergen avoidance, Matsui said. It also notes that multi-component avoidance strategies for dust mite and/or pet allergens have shown limited evidence of clinical benefit, but only in children. The National Asthma Education and Prevention Program also recommends that a comprehensive, multi-faceted approach to allergen avoidance be utilized if there is a plan of intervening environmentally.

In 1 of the negative studies exploring the effect of pest management intervention for mouse allergens on children with asthma, which Matsui led, there were no differences in clinical outcomes or mouse allergen exposure outcomes—both resulted in roughly 70% reductions in mouse allergen levels in the home. Both the intervention and education groups observed reductions in symptoms and morbidity.

“Many children—about 40%&mdash;still had allergen levels that were associated with morbidity,” Matsui said. “So new intervention strategies are needed.”

Matsui noted however, that single-allergen targeting can be promising when it is population-based and substantial. “A large reduction in home mouse allergen is feasible, and likely necessary, to achieve a significant clinical benefit,” she said.

All told, Matsui noted that the next steps for environmental interventions are to alter health care delivery and payment reform, to develop population-level and policy-based interventions, and a framework for random clinical trial reporting.

“Interpreting environmental inventions in random clinical trials is challenging because of mediation by allergen reduction, and population heterogeneity,” she said. “But environmental inventions are effective among pediatric populations when the targeted exposure is reduced, and emerging evidence supports single allergen interventions.”

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