Association Between Allergen Exposure in Inner-City Schools and Asthma Morbidity Among Students

Abstract

Importance: Home aeroallergen exposure is associated with increased asthma morbidity in children, yet little is known about the contribution of school aeroallergen exposures to such morbidity.

Objective: To evaluate the effect of school-specific aeroallergen exposures on asthma morbidity among students, adjusting for home exposures.

Design, setting, and participants: The School Inner-City Asthma Study was a prospective cohort study evaluating 284 students aged 4 to 13 years with asthma who were enrolled from 37 inner-city elementary schools in the northeastern United States between March 1, 2008, and August 31, 2013. Enrolled students underwent baseline clinical evaluations before the school year started and were then observed clinically for 1 year. During that same school year, classroom and home dust samples linked to the students were collected and analyzed for common indoor aeroallergens. Associations between school aeroallergen exposure and asthma outcomes during the school year were assessed, adjusting for home exposures.

Exposures: Indoor aeroallergens, including rat, mouse, cockroach, cat, dog, and dust mites, measured in dust samples collected from inner-city schools.

Main outcomes and measures: The primary outcome was maximum days in the past 2 weeks with asthma symptoms. Secondary outcomes included well-established markers of asthma morbidity, including asthma-associated health care use and lung function, measured by forced expiratory volume in 1 second.

Results: Among 284 students (median age, 8 years [interquartile range, 6-9 years]; 148 boys and 136 girls), exposure to mouse allergen was detected in 441 (99.5%) of 443 school dust samples, cat allergen in 420 samples (94.8%), and dog allergen in 366 samples (82.6%). Levels of mouse allergen in schools were significantly higher than in students' homes (median settled dust level, 0.90 vs 0.14 µg/g; P < .001). Exposure to higher levels of mouse allergen in school (comparing 75th with 25th percentile) was associated with increased odds of having an asthma symptom day (odds ratio, 1.27; 95% CI, 1.05-1.54; P = .02) and 4.0 percentage points lower predicted forced expiratory volume in 1 second (95% CI, -6.6 to -1.5; P = .002). This effect was independent of allergic sensitization. None of the other indoor aeroallergens were associated with worsening asthma outcomes.

Conclusions and relevance: In this study of inner-city students with asthma, exposure to mouse allergen in schools was associated with increased asthma symptoms and decreased lung function. These findings demonstrate that the school environment is an important contributor to childhood asthma morbidity. Future school-based environmental interventions may be beneficial for this important public health problem.

Figure 1. Association of Increasing Mouse Allergen Exposure in School and Asthma Symptoms

A, Children sensitized to mouse allergen and not sensitized to mouse allergen (P = .69 for interaction effect). B, Exposure to mouse allergen in school and asthma symptoms regardless of sensitization (P = .02). All models adjusted for age, sex, race/ethnicity, use of medication to control asthma, linked mouse allergen exposure at home, linked endotoxin exposure at school, and time of year of allergen collection. Asthma symptom days: maximum number of days during the previous 2 weeks with daytime wheezing, chest tightness, or cough; days on which child had to slow down or discontinue play activities owing to wheezing, chest tightness, or cough; or nights with wheezing, chest tightness, or cough leading to disturbed sleep.

Figure 2. Association of Increasing Mouse Allergen Exposure in School and Decline in Lung Function

Exposure to increasing levels of mouse allergen in schools was associated with a decrease in forced expiratory volume in 1 second (FEV₁) (P = .002). Adjusted for age, sex, race/ethnicity, use of medication to control asthma, linked mouse allergen exposure at home, linked endotoxin exposure at school, and time of year of allergen collection.