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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.
Sheehan et al. (Mon,) studied this question.