Normal Lung Function and Mortality in World Trade Center Responders and NHANES III Participants

Rationale: Low forced expiratory volume at one second (FEV1) is a biomarker of increased mortality. The association of normal lung function and mortality is not well described. Objective: To evaluate the FEV1-mortality association among participants with normal lung function. Methods: 10,999 Fire Department of the City of New York (FDNY) responders and 10,901 NHANES III participants, ages 18-65 with FEV1 ≥80% predicted, were analyzed, with FEV1 percent predicted calculated using Global Lung Function Initiative Global race-neutral reference equations. Mortality data were obtained from linkages to the National Death Index. Cox proportional hazards models estimated the association between FEV1 and all-cause mortality, controlling for age, sex, race/ethnicity, smoking history, and, for FDNY, work assignment. Cohorts were followed for a maximum of 20.3 years. Measurements and Main Results: We observed 504/10,999 deaths (4.6%) for FDNY and 1,237/10,901 deaths (9.4% [weighted]) for NHANES III. Relative to FEV1 ≥120% predicted, mortality was significantly higher for FEV1 100-109%, 90-99%, and 80-89% predicted in the FDNY cohort. In the NHANES III cohort, mortality was significantly higher for FEV1 90-99% and 80-89% predicted. Each 10% higher predicted FEV1 was associated with 15% (HR=0.85, 95% CI 0.80-0.91) and 23% (HR=0.77, 95% CI 0.71-0.84) lower mortality for FDNY and NHANES III, respectively. Conclusions: In both cohorts, higher FEV1 is associated with lower mortality, suggesting higher FEV1 is a biomarker of better health. These findings demonstrate that a single cross-sectional measurement of FEV1 is predictive of mortality over two decades, even when FEV1 is in the normal range.