Low grade systemic inflammation and lung function outcomes in European adults from the global asthma and allergy network of excellence (GA ² LEN) follow-up survey

Background Low grade systemic inflammation may intefere with maintenance of lung function. We have investigated the association between serum inflammatory markers and lung function in European adults. Methods The study sample was drawn from the GA 2 LEN screening survey, in which 55,000 adults aged 15 to 75 answered a questionnaire on respiratory symptoms. A stratified random sample was obtained for follow-up. 1,670 participants performed pre- and post- bronchodilator spirometry. Forced vital capacity (FVC), the ratio between the forced exhaled volume in 1 second (FEV1) and FVC (FEV 1 /FVC), FVC below lower limit of normal (FVC<LLN) and FEV 1 /FVC<LLN were calculated. Serum levels of C-reactive protein (CRP), Interleukin 6 (IL-6), Interleukin 8 (IL-8), Tumor Necrosis Factor alpha (TNFα), Transforming Growth Factor b (TGF-β) and Myeloperoxidase (MPO) were measured. Lung function and exposures were weighted to obtain estimated population parameters. Associations were investigated with linear regressions. Results CRP and IL-6 were negatively associated with FVC (adjusted effect size per doubling (95% Confidence Interval [CI] -0.05 (-0.08 to -0.03) and -0.09 (-0.14 to -0.04), respectively) and CRP was positively related to a higher prevalence of FVC<LLN (OR per doubling 1.29 (95% CI 1.04 to 1.61). CRP, IL-6 and MPO were positively associated with FEV 1 /FVC<LLN (Odds Ratios [OR] per doubling [95% CI] 1.37 [1.11 to 1.70]; 1.73 [1.14 to 2.64]; and 1.22 [1.00 to 1.48], respectively. Conclusion A better FVC was associated with lower levels of CRP and IL-6. CRP, IL-6 and MPO were associated with a higher prevalence of lung obstruction.