Indexed on: 04 Nov '17Published on: 04 Nov '17Published in: Annals of the American Thoracic Society
Rescue/recovery work at the World Trade Center (WTC) disaster site caused a proximate decline in lung function in Fire Department of the City of New York (FDNY) firefighters. A subset of this cohort experienced an accelerated rate of lung function decline over 15 years of post-9/11 follow-up.To determine if post-exposure inflammatory cell concentrations are biomarkers for subsequent forced expiratory volume (FEV1) decline and incident airflow limitation.Individual rates of FEV1 change were calculated for 9,434 firefighters using 88,709 spirometric measurements taken between 9/11/2001 (9/11) and 9/10/2016. We categorized FEV1 change rates into three trajectories: accelerated FEV1 decline (FEV1 loss >64 ml/year), expected FEV1 decline (FEV1 loss between 0-64 ml/year), and improved FEV1 (positive rate of change >0 ml/year). Occurrence of FEV1/FVC<0.70 after 9/11 defined incident airflow limitation. Regression models assessed associations of post-9/11 blood eosinophil and neutrophil concentrations with subsequent FEV1 decline and airflow limitation, adjusted for age, race, smoking, height, WTC exposure level, weight change and baseline lung function.Accelerated FEV1 decline occurred in 12.7% of participants (1,199/9,434), while post-9/11 FEV1 improvement occurred in 8.3% (780/9,434). Eosinophil and neutrophil concentrations were both associated with accelerated vs. expected FEV1 decline after adjustment for covariates (OR: 1.10 per 100 eosinophils/µl, 95% CI: 1.05-1.15 and OR: 1.10 per 1,000 neutrophils/µl, 95% CI: 1.05-1.15). Multivariable-adjusted linear regression models showed that neutrophil concentration was associated with FEV1 decline rate (1.14 ml/year decline per 1000 neutrophils/µl, 95% CI: 0.69-1.60 ml/year, p<0.001), while eosinophil concentration was associated with FEV1 decline rate in ever-smokers (1.46 ml/year decline per 100 eosinophils/µl, 95% CI: 0.65-2.26 ml/year, p<0.001) but not in never-smokers (p for interaction=0.004). Eosinophil concentration was also associated with incident airflow limitation (adjusted HR: 1.10 per 100 eosinophils/µl, 95% CI: 1.04-1.15). Compared with the expected FEV1 decline group, individuals experiencing accelerated FEV1 decline were more likely to have incident airflow limitation (adjusted OR: 4.12, 95% CI: 3.30-5.14).Elevated post-9/11 blood inflammatory cell concentrations were risk factors for subsequent accelerated FEV1 decline in WTC-exposed firefighters. Accelerated FEV1 decline was associated with incident airflow limitation, suggesting progressive airway injury in this subgroup.