Study: Asthma Associated with Indoor Allergen Sensitization

In urban populations, asthma morbidity has been associated with sensitization and exposure to indoor allergens in recent studies. However, few studies have focused on the Chicago region or included patients with and without asthma.

Due to the lack of Chicago-based asthma studies, a team of investigators assessed adult and pediatric patients in Chicago in order to confirm that sensitization to mouse urine, cockroaches, or dust mites is associated with increased odds of having asthma and increased asthma severity.

From June 2015 through December 2016, investigators conducted a retrospective chart review of 718 patients ages 1-90 years old seen at a Chicago public hospital who underwent in-vitro aeroallergen testing. Patient demographics, aeroallergen sensitivities, physician-diagnosed asthma, and asthma severity included the data collected, which was analyzed using chi-square tests.

In the study—presented at the American Academy of Allergy, Asthma & Immunology (AAAAI) 2019 Annual Meeting in San Francisco, CA—440 of 718 (61%) patients had a diagnosis of asthma, and a total of 341 out of 718 (47.5%) patients were sensitized to at least 1 of the 3 allergens studied.

Having asthma (OR 1.69; P< .001) was associated with sensitization to 1 or more allergens. Having sensitization to the individual allergens—mouse (OR 3.52; P< .001), cockroach (OR 1.49; P= .02), and dust mite (OR 1.56; P= .01)—were also associated with sensitization to 1 or more allergens.

Among their results, the team found a large number of the mouse-sensitized patients had a diagnosis of asthma (82/99 [82.5%]) even though only 99 (13.8%) asthma patients were sensitized to mice.

Consequently, the team concluded that having moderate or severe asthma (OR 2.38; P= .005) was more likely among persistent patients sensitized to cockroaches. However, asthma severity did not correlate with sensitization to mouse urine or dust mites.

This research only further adds to previous studies that point out the need for more allergen reduction guidelines. In clinical trials examining asthma outcomes, a wide variety of interventions designed to reduce allergens have been studied, but the likelihood of asthma has been shown to increase with the greater the complexity of the environment.

More specifically, factors are vast and include an expanding list of environmental factors that come with a low-income house that must be considered, such as greater numbers of cockroaches, other pests, less maintenance of carpeting, bedding, and much more.

In the study that consisted of an extensive meta-analysis of 59 randomized controlled trials and 8 non-randomized controlled trials, investigators found that there were some multicomponent interventions that did show some benefit in reducing allergens including air purification multicomponent context, carpet removal multicomponent, HEPA filter, vacuum multicomponent, mattress cover multicomponent, and pest control multicomponent.

However, absolutely none of the studies to date provided strong clinical control of asthma.

Primarily though, there are costs and potential downsides to any of these strategies that are not really considered within any of the studies.

As a result, the team noted that the evidence is inconclusive due to a lack of studies, which are greatly needed.

The authors noted that they would like to know more about the home and personal situation of the individual patients, and that the downsides to any recommendations need more attention and consideration as well.

The study, “Indoor Allergen Sensitization Correlates with Asthma in Chicago Public Hospital Patients,” was published online in The Journal of Allergy and Clinical Immunology.