Supplementary Material for: Impact of transitioning from Race-specific to Race-neutral GLI equation on lung function in a predominantly Caucasian population

Introduction Diagnosis and treatment decisions for many respiratory diseases are based on spirometric values. We compared the impact of changing the reference equations from GLI-2012 (race-specific) to GLI-2022 (race-neutral) in a predominantly Caucasian urban population. Methods PneumoLaus is a sub-study of CoLaus|PsyCoLaus, an ongoing prospective observational study conducted in Lausanne, Switzerland. Participants performed spirometry at baseline (2014-2017) and at follow-up (2018-2021, FU). We analysed changes of %predicted values (PV) for Forced Expiratory Volume in One second (FEV1) and Forced Vital Capacity (FVC) by comparing the GLI-2022 reference equation to GLI-2012. Sub-group analyses were performed for social class, sex and age using paired t-tests corrected by Holm-Bonferroni. We analysed the association of age, sex and social class on the differences using linear regression. Results A total of 3330 participants were included at baseline and 2005 at FU, >97% Caucasian. Employing GLI-2022 equations, the %PV increased significantly for both FEV1 (4.2%PV and +0.31 Z-score baseline, 4.6%PV and +0.28 Z-score FU, both p<0.0001) and FVC (4.9%PV and +0.34 Z-score baseline, 5.6%PV and + 0.29 Z-score FU, both p<0.0001). Younger individuals, males, and participants with only compulsory school education experienced the greatest increase. The prevalence of low FEV₁ and low FVC decreased using GLI-2022 references, while the prevalence of obstructive ventilatory impairment increased at baseline and FU (all p<0.05). Discussion In this predominantly Caucasian urban population-based cohort, applying GLI-2022 equations led to a general FEV1 and FVC %PV increase, particularly among younger individuals, males, and participants with only compulsory school education. Applying GLI-2022 equations also led to a general FEV1 and FVC z-score increase. These findings changes may carry relevant implications for clinical care and social policy decisions.