Visit-to-Visit FEV1 Variation and Mortality in New York City Fire Department Rescue and Recovery Workers Exposed to World Trade Center Collapse–Related Dust

<b>Rationale:</b> Forced expiratory volume in 1 second (FEV₁) and its longitudinal change are mortality risk factors. Visit-to-visit FEV₁ variation is a risk factor for death in cystic fibrosis but has not been studied in other cohorts. <b>Objectives:</b> We sought to assess whether longitudinal visit-to-visit FEV₁ variation is a mortality risk factor in rescue and recovery workers in the Fire Department of New York who were exposed to dust related to the collapse of the World Trade Center on September 11, 2001 (9/11/2001). <b>Methods:</b> Linear mixed-effects regression of all post-9/11/2001 FEV₁ measurements defined the time effect on longitudinal FEV₁ decline (FEV₁ slope) and its standard error (visit-to-visit FEV₁ variation). Cox proportional hazards and logistic models adjusted for age and smoking assessed the association between FEV₁-related risk factors and mortality. Receiver operating characteristic area under the curve (AUC) assessed predictive model performance. <b>Results:</b> Among 11,745 workers with three or more FEV₁ measurements, 575 (4.9%) died. When all FEV₁-related risk factors were combined, each 5-ml/yr increase in visit-to-visit FEV₁ variation increased mortality 2.1-fold (hazard ratio [HR] = 2.14; 95% confidence interval [CI] = 1.84-2.48); each 10% predicted reduction in the last longitudinal FEV₁ increased mortality 15% (HR = 1.15; 95% CI, 1.09-1.21), but each 10-ml/yr longitudinal FEV₁ decline was not associated with mortality (HR = 1.04; 95% CI, 0.99-1.10). The receiver operating characteristic AUC of a fully adjusted multivariable cumulative mortality model was 0.82 (95% CI, 0.80-0.84); for unadjusted visit-to-visit FEV₁ variation, the AUC was 0.80 (95% CI, 0.78-0.82); for last longitudinal FEV₁, the AUC was 0.61 (95% CI, 0.59-0.64); and for longitudinal FEV₁ decline, the AUC was 0.58 (95% CI, 0.56-0.61). In the ratio of participants with high exposure/total number of participants (1,988/11,745; 16.9%), among patients with high exposure, defined as arrival at the World Trade Center site before noon on 9/11/2001, the risk of high visit-to-visit FEV₁ variation (top quartile, ⩾10.35 ml/yr) increased 25% (odds ratio = 1.25; 95% CI, 1.12-1.40). <b>Conclusions:</b> Visit-to-visit FEV₁ variation is a mortality risk factor in rescue and recovery workers in the Fire Department of New York City, with greater accuracy for predicting cumulative mortality than either last longitudinal FEV₁ or longitudinal FEV₁ decline. Further investigation in other cohorts is needed to assess the generalizability of this rarely studied mortality risk factor.