Spirometry
In the 2018 study, all participants who were contacted for response confirmation were invited for spirometry at the Pediatric Respiratory Unit of the University Hospital of Patras. Measurements were performed from June 18 to September 7, 2018 using a Micro 5000 spirometer (Medisoft, Sorinnes, Belgium) according to the established guidelines20,21. All children who performed spirometry were free of respiratory symptoms and had interrupted asthma medication for at least four weeks. Forced expiratory volume at 1 s (FEV1), forced vital capacity (FVC), FEV1/FVC ratio, and forced expiratory flow between 25 and 75% of FVC (FEF25-75) values were assessed according to Global Lung Initiative normative data22.