Examining the relationship of nitrogen dioxide and obesity on asthma outcomes

Nitrogen dioxide is a common air pollutant and can be found in elevated levels in metropolitan areas due to traffic congestion. Air pollutants have been shown to impact the development of asthma in childhood. A report in the Journal of Allergy and Clinical Immunology examines the relationship between nitrogen dioxide and asthma symptoms and morbidity by body mass index category as well as the impact of the asthma symptoms.¹

The researchers used the School Inner-City Asthma Study, which enrolled students aged 4 to 13 years who had asthma and attended 37 inner-city schools. There was a baseline determination of each student’s body mass index percentile. Following enrollment into the study, asthma symptoms, lung function, pulmonary inflammation, and morbidity were watched through the next academic year. Classroom nitrogen dioxide data, which was linked to enrolled students, were collected twice per year.

There were 271 students included in the analyses and the cohort was predominantly Black and hispanic. In the cohort, 50% of the children were normal weight (5-84th body mass index percentile); 15% were overweight (≥85-94th body mass index percentile); and 35% obese (≥95th body mass index percentile). The investigators found that for each 10-part per billion increase in nitrogen dioxide, students who were obese had a significant increase in the odds of having an asthma symptom day (odds ratio [OR], 1.86; 95% CI, 1.15-3.02) as well as in days that a caregiver had to change plans (OR, 4.24; 95% CI, 2.33-7.70). This was quite different from students who were normal weight and showed no link between nitrogen exposure and symptom days (OR, 0.90; 95% CI, 0.57-1.42; pairwise interaction P = .03) as well as change in caregiver plans (OR, 1.37; 95% CI, 0.67-2.82; pairwise interaction P = .02). Additionally, the relationship between lung function, fractional exhaled nitric oxide, and nitrogen dioxide levels had no difference between body mass index.

The researchers concluded that it seems like children who have an obese body mass index are more vulnerable to the effects of classroom exposure to nitrogen dioxide in the classroom and the impact on asthma symptoms. Targeting indoor levels of nitrogen dioxide in schools could help improve asthma outcomes for children who are obese.

Reference

1. Permaul P, Gaffin J, Petty C, et al. Obesity may enhance the adverse effects of NO2 exposure in urban schools on asthma symptoms in children. Journal of Allergy and Clinical Immunology. 2020;146(4):813-820. doi:10.1016/j.jaci.2020.03.003