Increased Airway Wall Thickness is Associated with Adverse Longitudinal First-Second Forced Expiratory Volume Trajectories of Former World Trade Center workers.

RATIONALE

Occupational exposures at the WTC site after September 11, 2001 have been associated with several presumably inflammatory lower airway diseases. In this study, we describe the trajectories of expiratory air flow decline, identify subgroups with adverse progression, and investigate the association of a quantitative computed tomography (QCT) imaging measurement of airway wall thickness, and other risk factors for adverse progression.

METHODS

We examined the trajectories of expiratory air flow decline in a group of 799 former WTC workers and volunteers with QCT-measured (with two independent systems) wall area percent (WAP) and at least 3 periodic spirometries. We calculated individual regression lines for first-second forced expiratory volume (FEV), identified subjects with rapidly declining and increasing ("gainers"), and compared them to subjects with normal and "stable" FEV decline. We used multivariate logistic regression to model decliner vs. stable trajectories.

RESULTS

The mean longitudinal FEVslopes for the entire study population, and its stable, decliner, and gainer subgroups were, respectively, - 35.8, - 8, - 157.6, and + 173.62 ml/year. WAP was associated with "decliner" status (OR 1.08, 95% CI 1.02, 1.14, per 5% increment) compared to stable. Age, weight gain, baseline FEV percent predicted, bronchodilator response, and pre-WTC occupational exposures were also significantly associated with accelerated FEV decline. Analyses of gainers vs. stable subgroup showed WAP as a significant predictor in unadjusted but not consistently in adjusted analyses.

CONCLUSIONS

The apparent normal age-related rate of FEV decline results from averaging widely divergent trajectories. WAP is significantly associated with accelerated air flow decline in WTC workers.