Air pollution and ethnicity associated with prevalence of small airways obstruction in a Caucasian population-based study

Introduction: Larger population-based studies on the prevalence and risk factors associated with small airway obstruction (SAO) are lacking. Recently, evidence from China associated exposure to particulate matter of size ≤2.5 µm (PM2.5) as a potential risk factor for SAO whose prevalence was high (43.5%). In our study, we hypothesized that lesser air pollution levels were associated with a lower prevalence of SAO in Switzerland. Methods: PneumoLaus is based on the CoLaus cohort that phenotyped a random population sample in Lausanne, Switzerland. SAO was defined by maximum mid-expiratory flow (MMEF) <65% of predicted value (PV) or MMEF Results: Overall, 3’351 individuals performed spirometry (97.6% Caucasian), of which 12.7% (n=425) had MMEF<65%PV and 5.0% (n=167) MMEF65 years only for MMEF<65%PV. The national average ambient PM2.5 concentration was 14.1 µg/m3 in 2010 and 6.3 µg/m3 in Lausanne in 2017. Conclusion: Utilizing the MMEF <65%PV criteria can lead to SAO overdiagnosis in elderly individuals. The prevalence ≤12.7% of SAO in our study compared to data from Asia could be related to lower PM2.5 exposure and/or ethnicity. Our results highlight the need for strategies focused on air quality as a determinant for respiratory health.