Background The aetiology of chronic rhinosinusitis (CRS) is multifactorial with a complex interplay between environmental, microbial endogenous and genetic factors. The impact of outdoor air pollution on prevalence or severity of CRS remains largely unknown. Methods Real-life geolocation data (2017–2018, Belgium) from 278 CRS patients (2576 health records) using the mySinusitisCoach mobile application were analysed to calculate the patients’ individual exposure to outdoor air pollutants (ozone (O3), black carbon (BC), nitrogen dioxide (NO2) and particulate matter with diameter < 2.5 μm (PM2.5)) and to associate these pollutants with the patients’ sinus related symptoms measured at multiple occasions by visual analogue scale (VAS). Results The adjusted seasonal model for the spring–summer (n = 1000 health entries, N = 83 patients) population revealed an increase of 6.07 (p < 0.0001) in overall CRS symptom scoring for an interquartile range (IQR) increase in exposure to O3 (26.9 μg/m3). An increase of 1.69 (p = 0.05) in total CRS symptom scoring was observed for an IQR increase of PM2.5 (7.1 µg/m3) exposure. Sex-stratified analysis in the spring–summer population showed significant interaction between air pollution and sex with male patients having higher total CRS symptom scores for an IQR increase in exposure to PM2.5 (3.52, p = 0.001), and O3 (8.33, p < 0.0001), while no significant association with symptom severity was seen in the female patients. In the analysis stratified by comorbid asthma, CRS patients with comorbid asthma had higher total CRS symptoms for an IQR increase in exposure to PM2.5 (2.58, p = 0.04) and O3 (7.72, p < 0.0001) while the patients without comorbid asthma had no significant symptom increases. Conclusion Exposure to outdoor air pollution is associated with increased symptom severity in CRS patients. The extent to which CRS patients are sensitive to outdoor air pollution exposure varies per season and depends on their sex and comorbid asthma status. mHealth technology has the potential to reveal novel insights on the patients’ exposome and disease severity in the real-life situation.

Background: The aetiology of chronic rhinosinusitis (CRS) is multifactorial with a complex interplay between environmental, microbial endogenous and genetic factors. The impact of outdoor air pollution on prevalence or severity of CRS remains largely unknown. Methods: Real-life geolocation data (2017-2018, Belgium) from 278 CRS patients (2576 health records) using the mySinusitisCoach mobile application were analysed to calculate the patients’ individual exposure to outdoor air pollutants (ozone (O3), black carbon (BC), nitrogen dioxide (NO2) and particulate matter with diameter <2.5 μm (PM2.5)) and associate these pollutants with the patients’ sinus related symptoms measured at multiple occasions by visual analogue scale (VAS).Results: The adjusted seasonal model for the spring-summer (n=1000 health entries, N=83 patients) population revealed an increase of 6.07 (p<0.0001) in overall CRS symptom scoring for an interquartile range (IQR) increase in exposure to O3 (26.9 μg/m3). An increase of 1.69 (p=0.05) in total CRS symptom scoring was observed for an IQR increase of PM2.5 (7.1 µg/m3) exposure. Gender-stratified analysis in the spring-summer population showed significant interaction between air pollution and gender with male patients having higher total CRS symptom scores for an IQR increase in exposure to PM2.5 (3.52, p=0.001), and O3 (8.33, p<0.0001), while no significant association with symptom severity was seen in the female patients. In the analysis stratified for comorbid asthma, CRS patients with comorbid asthma had higher total CRS symptoms for an IQR increase in exposure to PM2.5 (2.58, p=0.04) and O3 (7.72, p<0.0001) while the patients without comorbid asthma had no significant symptom increases. Conclusion: Exposure to outdoor air pollution is associated with increased symptom severity in CRS patients. The extent to which CRS patients are sensitive to outdoor air pollution exposure varies per season and depends on their gender and comorbid asthma status. mHealth technology has the potential to reveal novel insights on the patients’ exposome and disease severity in the real-life situation.