Interaction between air pollution and pollen seasons on allergic rhinitis control

Abstract

A few studies have suggested an interaction between air pollution and pollen exposure on allergy symptoms but more research is needed. As part of the POLLAR (Impact of Air Pollution in Asthma and Rhinitis) project, we investigated the associations between major air pollutants (ozone and PM2.5) and allergic rhinitis control, during grass and birch pollen seasons, using the Allergy Diary app (a validated mHealth tool for allergic rhinitis management). The daily impact of allergic symptoms was recorded, using visual analogue scale (VAS), by 3,328 geolocated app users in 2017 and 2018 in Northern Europe, representing 36,523 VAS days. Uncontrolled allergic rhinitis was defined either as 1) VAS≥50, 2) VAS≥35 with intra-nasal corticosteroids or azelastine-fluticasone propionate use or 3) VAS≥20 and use of ≥3 allergic rhinitis medications. For each VAS recorded with geolocation, pollutants levels were assessed using the SILAM (System for integrated modelling of atmospheric composition) database, and pollen seasons were assessed by regions using Google Trends. Generalized estimating equation models were used to account for repeated measures per user, adjusting for gender, age, treatment and country. Positive associations were found between ozone and uncontrolled allergic rhinitis during the grass pollen season only (ORs=1.25 [1.11-1.41] and 1.14 [1.04-1.25], per interquartile range increase in ozone, for 2017 and 2018 respectively). A similar trend was found for PM2.5 levels in 2017 while results for 2018 did not suggest any effect modification by pollen seasons. These results show the importance of air pollution and allergen concentrations, and their interaction, as predictors of allergic rhinitis control.