Abstract
BACKGROUND: Elevated blood eosinophils have been associated with lower lung function and are believed to be associated with accelerated lung function decline. METHOD: Blood eosinophils were measured in four cohorts: <45 years cohort within the Vlagtwedde-Vlaardingen (V&V) study, the Uppsala cohort of the European Community Respiratory Health Survey (ECRHS-Uppsala; <45 years), ≥45 years cohort within the V&V study, and the Rotterdam study (≥45 years). Blood eosinophils at baseline were classified as normal (<300 cells·μL(-1)) or elevated (≥300 cells·μL(-1)). Lung function was measured at baseline and follow-up with spirometry: forced expiratory volume in 1 s (FEV(1)), vital capacity (VC) and their ratio FEV(1)/VC. The association between blood eosinophils and lung function was tested cross-sectionally using linear regression and longitudinally using a mixed model, both adjusted for age, sex, height, pack-years smoking and smoking status. Stratified analyses were done for asthma. RESULTS: Elevated blood eosinophils were associated with lower FEV(1) (regression coefficient -147 mL (95% CI -188 to -105 mL)), VC (-120 mL (-165 to -75 mL)) and FEV(1)/VC (-1.3% (-1.9% to -0.6%)) at baseline in the two <45 years cohorts, and with lower FEV(1) (-70 mL (-112 to -27 mL)) and FEV(1)/VC (-1.8% (-2.6% to -1.0%)) in the two ≥45 years cohorts. Elevated blood eosinophils were associated with an accelerated decline in FEV(1) (-5.5 mL·year(-1) (95% CI -10.5 to -0.5 mL·year(-1))) and VC (-6.4 mL·year(-1) (-11.26 to -1.5 mL·year(-1))) compared to normal blood eosinophils in the younger asthmatic subjects in the longitudinal studies. CONCLUSION: Elevated blood eosinophils are associated with lower lung function in the general population and with an accelerated lung function decline among asthmatic individuals.