Annual decline in forced expiratory volume and airway inflammatory cells and mediators in a general population-based sample

Background: Few studies have examined the relationships between sputum inflammatory markers and subsequent annual decline in forced expiratory volume in 1 s (dFEV₁). This study investigated whether indices of airway inflammation are predictors of dFEV₁ in a general population-based sample.

Methods: The study, conducted from 2003 to 2005, included 120 healthy Norwegian subjects aged 40 to 70 years old. At baseline, the participants completed a self-administered respiratory questionnaire and underwent a clinical examination that included spirometry, venous blood sampling, and induced sputum examination. From 2015 to 2016, 62 (52%) participants agreed to a follow-up examination that did not include induced sputum examination. Those with a FEV₁/forced vital capacity (FVC) ratio < 0.70 underwent a bronchial reversibility test. The levels of cytokines, pro-inflammatory M1 macrophage phenotypes were measured in induced sputum using bead-based multiplex analysis. The associations between cytokine levels and dFEV₁ were then analysed.

Results: The mean dFEV₁ was 32.9 ml/year (standard deviation 26.3). We found no associations between dFEV₁ and the baseline indices of sputum inflammation. Seven participants had irreversible airflow limitation at follow-up. They had lower FEV1 and gas diffusion at baseline compared with the remaining subjects. Moreover, two of these individuals had a positive reversibility test and sputum eosinophilia at baseline.

Conclusions: In this cohort of presumably healthy subjects, we found no associations between sputum inflammatory cells or mediators and dFEV₁ during 10 years of follow-up.