Prevalence of small airway dysfunction in the Swiss PneumoLaus Cohort.

Background: Recent evidence identified exposure to particulate matter of size ≤2.5 µm (PM) as a risk factor for high prevalence of small airway dysfunction (SAD). We assessed the prevalence of SAD in a European region with low air pollution levels.

Methods: SAD was defined as a maximum mid-expiratory flow (MMEF) <65% of predicted value (PV) or MMEF
Results: Among 3351 participants (97.6% Caucasian, 55.7% female sex, mean age 62.7 years), we observed MMEF <65% PV in 425 (12.7%) and MMEF 65 years only. In an area where ambient PM concentration was <15 µg·m during the observation period (2010 and 2020), ≥72% of participants with SAD were ever-smokers.

Conclusions: The observed low prevalence of SAD of 5.0-12.7% depending on criteria employed may be related to lower PM exposure. Smoking was the main factor associated with SAD in an area with low PM exposure. Employing a MMEF threshold <65% PV carries a risk of SAD overdiagnosis in elderly individuals.