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Mouse allergen in inner-city schools linked to asthma morbidity among children
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Decreased lung function and increased asthma symptoms in children were associated with elevated levels of mouse allergen in urban elementary and middle schools, according to a recently published study.
“Asthma affects a large proportion of children in the United States, accounting for more than 14 million missed school days per year and costing billions of dollars in health care use,” William J. Sheehan, MD, assistant in medicine at Boston Children’s Hospital and instructor in pediatrics at Harvard Medical School, and colleagues wrote.
“Furthermore, asthma morbidity disproportionately affects minorities and low-income groups in inner-city neighborhoods. [However] to our knowledge there are no comprehensive studies evaluating asthma outcomes resulting from allergen exposure in schools, where children spend most of their day.”
To evaluate the role of indoor allergens specific to school environments on asthma morbidity in urban areas, Sheehan and colleagues conducted the School Inner-City Asthma Study that included children aged 4 to 13 years attending inner-city public schools in the northeastern region of the U.S. The 5-year study included 284 children (148 boys) from 37 schools diagnosed with asthma for 1 year or more and used preventive medication daily, wheezed and had had an unscheduled physician visit for asthma in the last year. Students were observed randomly over 1 year each during the study period, and parents completed screening questionnaires in the spring and participated in follow-up telephone interviews at 3, 6, 9 and 12 months after spirometry.
The researchers defined sensitization as a wheal 3 mm or larger on aeroallergen skin testing screening (MultiTest device; Lincoln Diagnostics, Linden, NJ) or a specific immunoglobulin level of 0.35 kU/L or greater on serum testing (ImmunoCAP; Phadia AB). In addition, the researchers collected classroom-settled dust samples twice during the academic year in each participating school. Among the collected indoor aeroallergens were cockroach, cat, dog, mouse, dust mite and rat analyzed by MARIA (Indoor Biotechnologies). Moreover, the detection rates were adjusted for home exposures.
Interaction effect analysis showed that mouse allergen was the most commonly detected allergen in both homes (96%) and schools (99.5%). Cat allergen was detected in 94.8% of schools and homes and dog allergen was detected in 82.6% of schools and homes in participating students. Mouse allergen detection in schools was significantly increased compared with exposure in students’ homes (median settled dust level, 0.9 vs. 0.14 µg/g). Further, mouse allergen shared a correlation with increased odds of a student exhibiting asthma symptoms including wheezing, coughing and tightness of chest (OR = 1.27; 95% CI, 1.05-1.54) and a 4% point lower predicted forced expiratory volume in 1 second (95% CI, –6.6 to –1.5).
“Students who were both sensitized and exposed to elevated levels of mouse allergen did exhibit increased asthma morbidity; however, we were surprised to find an association irrespective of sensitization status,” the researchers wrote. “We considered endotoxin as a possible confounder based on prior reports that nonallergic symptomatic effect in mouse research workers occurs owing to airborne endotoxin exposure; however, our findings remained even after adjusting for endotoxin levels.” – by Kate Sherrer
Disclosure: This study was funded by NIH grants R01A073964, R01A073964-0251, K24AI106822, K23AI106945, K23ES023700, ES-000002. The researchers report no relevant financial disclosures.
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