Obesity may enhance the adverse effects of NO exposure in urban schools on asthma symptoms in children.

BACKGROUND

Sparse data address the effects of nitrogen dioxide (NO) exposure in inner-city schools on obese students with asthma.

OBJECTIVE

We sought to evaluate relationships between classroom NO exposure and asthma symptoms and morbidity by body mass index (BMI) category.

METHODS

The School Inner-City Asthma Study enrolled students aged 4 to 13 years with asthma from 37 inner-city schools. Students had baseline determination of BMI percentile. Asthma symptoms, morbidity, pulmonary inflammation, and lung function were monitored throughout the subsequent academic year. Classroom NO data, linked to enrolled students, were collected twice per year. We determined the relationship between classroom NO levels and asthma outcomes by BMI stratification.

RESULTS

A total of 271 predominantly black (35%) or Hispanic students (35%) were included in analyses. Fifty percent were normal weight (5-84th BMI percentile), 15% overweight (≥85-94th BMI percentile), and 35% obese (≥95th BMI percentile). For each 10-parts per billion increase in NO, obese students had a significant increase in the odds of having an asthma symptom day (odds ratio [OR], 1.86; 95% CI, 1.15-3.02) and in days caregiver changed plans (OR, 4.24; 95% CI, 2.33-7.70), which was significantly different than normal weight students who exhibited no relationship between NO exposure and symptom days (OR, 0.90; 95% CI, 0.57-1.42; pairwise interaction P = .03) and change in caregiver plans (OR, 1.37; 95% CI, 0.67-2.82; pairwise interaction P = .02). Relationships between NO levels and lung function and fractional exhaled nitric oxide did not differ by BMI category. If we applied a conservative Holm-Bonferroni correction for 16 comparisons (obese vs normal weight and overweight vs normal weight for 8 outcomes), these findings would not meet statistical significance (all P > .003).

CONCLUSIONS

Obese BMI status appears to increase susceptibility to classroom NO exposure effects on asthma symptoms in inner-city children. Environmental interventions targeting indoor school NO levels may improve asthma health for obese children. Although our findings would not remain statistically significant after adjustment for multiple comparisons, the large effect sizes warrant future study of the interaction of obesity and pollution in pediatric asthma.