Cockroach, mouse allergens drive upper respiratory infections in children with asthma
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Key takeaways:
- Sensitizations among children with asthma included cockroach (56%) and mouse (59%).
- Children with upper respiratory infection outcomes had higher median concentrations of cockroach and mouse allergens.
Risks for respiratory viral infections increased among children with asthma who were exposed to high levels of floor cockroach and mouse airborne allergens, according to a study published in The Journal of Allergy and Clinical Immunology.
However, exposure to cat allergens appeared to have a protective effect, Darlene Bhavnani, PhD, MPH, department of population health, Dell Medical School, University of Texas at Austin, and colleagues wrote.
“There are large racial and ethnic disparities in asthma exacerbations among children,” Bhavnani told Healio. “We know that asthma exacerbations are largely driven by upper respiratory viral infections.”
Previously, Bhavnani and colleagues found large racial and ethnic disparities in upper respiratory infections (URIs) among children with asthma.
“Understanding the contextual factors that drive these racial and ethnic disparities in upper respiratory infections could help to inform our understanding of disparities in asthma exacerbations,” Bhavnani said.
Minoritized populations are often subject to poor living conditions such as pest exposure in their neighborhoods and homes, she continued.
“We set out to try to understand whether exposure to indoor allergens is associated with upper respiratory infections with and without symptoms,” Bhavnani said.
Study design, results
The randomized clinical trial used data from the Environmental Control as Add-on Therapy for Childhood Asthma study, including 90 children (median age, 9.5 years; 60% boys; 92% Black; 92% with public health insurance) aged 5 to 17 years with persistent asthma.
Sensitizations among the cohort included cockroach (56%), mouse (59%), cat (39%), dog (36%) and dust mite (35%), with 69% sensitized to two or more allergens.
All children had prescriptions for controller medications for their asthma, but none were using immunotherapy or biologics.
After an interview and clinic visit at baseline, clinic visits followed at 2, 4 and 6 months. Researchers conducted home environmental assessments up to 6 weeks after baseline and at 3 and 6 months. The study included 192 observations about URIs and environmental allergen concentrations during clinic and home visits.
Fifty-two of 191 observations (approximately 27%) indicated at least one respiratory virus in nasal mucus samples, including 33 (63%) positive for rhinovirus and 10 (19%) positive for respiratory syncytial virus. Also, 18 of 51 of these infections (35%) included common cold symptoms.
Among patients with a URI and cold symptoms, nine of 14 had fractional exhaled nitric oxide levels of 20 ppb or higher and nine of 17 had a percent-predicted FEV1 of less than 80%. Further, 29 of 190 observations (15%) included cold symptoms and 18 of 29 (62%) had a URI, both on average.
“Among children with asthma, exposure to cockroach and mouse allergens were positively associated with having a symptomatic viral infection,” Bhavnani said.
Median allergen concentrations included 0.4 U/g (interquartile range [IQR], 0.1-2.7) for cockroach, 590 ng/g (IQR, 119-2,960) for mouse and 84.5 ng/g (IQR, 25.2-1,530) for cat in settled floor dust and 3.03 pg/m3 (IQR, 0.85-15.7) for mouse in airborne samples.
Participants with outcomes associated with URIs had higher median concentrations of cockroach, airborne mouse and settled floor mouse allergens but not dog or cat. Odds for outcomes associated with URIs increased with increases in cockroach and airborne mouse allergen concentrations.
“It was interesting that stronger associations were observed for children who had positive allergy tests to cockroach and mouse allergens,” Bhavnani said.
There also were associations between each doubling in cockroach allergen and an 18% increase in the odds for a URI with cold symptoms (OR = 1.18; 95% CI, 0.99-1.4), a 31% increase in odds for a URI with cold symptoms and pulmonary eosinophilic inflammation (OR = 1.31; 95% CI, 1.1-1.57), and a 45% increase in odds for a URI with cold symptoms and lower lung function (OR = 1.45; 95% CI, 1.13-1.85).
Similarly, each doubling in airborne mouse allergen concentration was associated with a 12% increase in odds for a URI, a 14% increase in odds for a URI with cold symptoms, a 19% increase in odds for a URI with cold symptoms and pulmonary eosinophilic inflammation and a 27% increase in odds for a URI with cold symptoms and lower lung function, but the researchers did not consider these associations to be statistically significant.
The researchers also noted an increase in effect size based on odds ratios for cockroach as the severity of outcomes increased, such as from a URI to a URI with common cold symptoms and then lower respiratory outcomes.
To some extent, airborne mouse allergens saw a similar increase in effect size, the researchers said. Floor mouse allergens also had positive but less attenuated associations compared with airborne mouse allergens.
There were no associations between cat or dog allergens in floor dust and increased odds for outcomes associated with URIs. In fact, the researchers said that there were negative associations between cat allergen concentrations and some outcomes.
Adjustments for mouse allergen sensitivity and airborne mouse allergen concentrations in cat allergen models due to the negative correlation between cat and airborne mouse allergen concentrations (r = –0.12) did not alter the protective effects of cat allergen consistently in any outcomes.
Noting that the homes that had the highest concentrations of cat allergens also were more likely to have a cat than the homes with the lowest concentrations, the researchers said that these protective effects may be due to exposure to cat allergen or to direct exposure to the cat in the home. Additionally, the researchers said, microbial communities specific to homes with a cat may have protective effects, or small cell sizes may produce these effects.
“We did observe a negative association between cat and mouse allergen in homes suggesting that cats may keep mouse populations low,” Bhavnani said. “However, a cat allergy was very common among those with a mouse allergy, so owning a cat to keep mouse populations low may not be a viable strategy overall.”
There also were associations between a 38% increase in odds for a URI with cold symptoms and pulmonary eosinophilic inflammation (OR = 1.38; 95% CI, 1.14-1.67) and a 58% increase in odds for a URI with cold symptoms and lower lung function (OR = 1.58; 95% CI, 1.18-2.12) and a doubling in cockroach allergen among children sensitized to it.
“Exposure to pests, which is linked to living in disadvantaged neighborhoods, may put children with asthma who live in these neighborhoods — and who tend to be minoritized — at an increased risk of getting colds,” Bhavnani said. “We found that these colds don’t just affect their upper airways but also affect their lungs.”
Children who were not sensitized to cockroach allergen experienced attenuated associations, the researchers said, adding that airborne mouse and floor dog allergens had similar observations, although floor mouse and floor cat allergens were less so.
Conclusions, next steps
Based on these findings, the researchers said there were associations between allergen concentrations and increased risk for infection, common cold symptoms and lower respiratory tract effects among children with asthma.
Environmental protections that reduce exposures to mouse and cockroach as well as biologic therapies may decrease risks for virus-associated morbidity among these children, the researchers said.
“Physicians caring for minoritized children with asthma can help to advocate for healthy homes and healthy neighborhoods,” Bhavnani said. “Living in homes where pest infestations are not a problem may help to decrease the risk of viral-associated morbidity among children with asthma.”
Additional studies with larger cohorts that evaluate these associations through direct comparisons of allergen exposure with viral infections among Black and white children also may determine if allergens drive racial disparities in URI and asthma exacerbations associated with viruses, the researchers said.
“There are a number of contextual factors that may drive racial and ethnic disparities in viral infections among children with asthma,” Bhavnani said. “By better understanding the suite of contextual factors and how they relate to each other, we can better design interventions to reduce asthma morbidity in minoritized children with asthma.”
Reference:
- Indoor allergens worsen respiratory infections in children with asthma, study finds. https://www.eurekalert.org/news-releases/1057814. Published Sept. 12, 2024. Accessed Sept. 13, 2024.