Air Quality Metrics and Intervention Intervals for Idiopathic Subglottic Stenosis

Introduction: Idiopathic subglottic stenosis is a rare, chronic condition recently shown to rely on IL-17A signaling pathways. Exposure to PM2.5, diesel exhaust particles, ozone, and nitrogen oxides have all been linked to increases in IL-17A. However, no work to date has assessed for a link between these air quality factors and the severity of idiopathic subglottic stenosis.

Methods: Data from the Environmental Protection Agency (EPA) and North American Airway Collaborative (NoAAC) from 2016-2019 were gathered. Included patients had a diagnosis of idiopathic subglottic stenosis and had received an airway intervention. They were separated into groups based on whether or not they required further intervention, and if so how long after the initial intervention: within 6 months, within 6 months to 3 years, and greater than 3 years. Zip codes were used to link recurrence data to local air quality metrics measuring nitrogen dioxide, carbon monoxide, ozone, sulfur dioxide, PM2.5, PM10, and overall air quality index (AQI). EPA data was downloaded from the EPA website. Daily averages were calculated for each sensor and pollutant. These data were merged and analyzed using R version 4.2.2.

Results: 526 patients had zip codes within the USA allowing analysis with EPA data. No correlation between decreased time to intervention and increased levels of local air pollutants was found. Increased AQI was associated with no need for repeat intervention (p = 0.00000107), or increased intervals, as were increased ozone levels (p = 0.0022). No similar pattern was found with the other pollutants. Of note, there are more sensors for AQI and ozone than for the other pollutants.

Conclusions: Unlike the other pollutants, ozone is found in increased levels in rural areas. This may represent a different overall air quality environment for these patients. While no correlation could be found between the increased levels of other pollutants and the time to repeat intervention, the population is small and the intervention groupings are wide. Further research is required to further explore this correlation and identify environmental risk factors for this population.