Lung function decline after World Trade Center exposure raises risk for mortality

Key takeaways:

• Individuals who experienced drops in lung function after World Trade Center dust exposure faced an elevated risk for mortality.
• Lower baseline lung function also raised this population’s mortality risk.

Over time, reductions in lung function following exposure to World Trade Center dust heighten the risk for all-cause and cancer-cause mortality, according to results published in Annals of the American Thoracic Society.

“This study provides evidence that lung function decline is associated with all-cause mortality and cancer-cause mortality after controlling for important confounders,” David G. Goldfarb, PhD, epidemiologist at the Fire Department of the City of New York (FDNY) World Trade Center (WTC) Health Program, and colleagues wrote.

In a prospective cohort study, Goldfarb and colleagues analyzed 12,264 firefighters and emergency medical service providers (mean age, 39.7 years; 96.7% men; 63.8% never smoking status) exposed to WTC dust to determine how baseline prebronchodilator lung function and changes in lung function from baseline are linked to all-cause and cancer-cause mortality through Dec. 31, 2021.

Researchers used joint longitudinal survival models that accounted for several variables, including age, race/ethnicity, height, smoking, work assignment and WTC exposure, to observe each relationship.

Notably, a majority of the study population was firefighters (n = 10,301), with a smaller number of emergency service providers (n = 1,963).

Of the total cohort, 607 (4.9%) individuals died, with 190 individuals (1.5%) dying due to cancer. Other causes of death included those related to heart disease (n = 131) and those related to respiratory disease (n = 30), according to researchers.

In terms of lung function, more individuals had an FEV₁ of 80% predicted or more (normal) at baseline compared with the final measure of FEV₁ (89.4% vs. 81.5%). Between an individual’s first measure of lung function and the end of follow-up, researchers reported that an average of 19.1 years passed.

Individuals faced an elevated risk for both assessed mortality outcomes if they had a lower baseline FEV₁ (all-cause, HR per liter = 2.32; 95% CI, 1.98-2.72; cancer-cause, HR per liter = 1.99; 95% CI, 1.49-2.66). This finding was also true for heart disease-related death (HR per liter = 3.12; 95% CI, 2.23-4.35) and respiratory disease-related death (HR per liter = 5.67; 95% CI, 3.08-10.44).

When looking at the relationship between a 100 mL reduction in FEV₁ per year and death, researchers found that the risk for all-cause mortality went up by 11% (HR = 1.11; 95% CI, 1.06-1.15) and the risk for cancer-cause mortality went up by 7% (HR = 1.07; 95% CI, 1-1.15) with every drop.

“This investigation ... revealed a significant association of FEV₁ decrease and cancer-cause mortality, findings that are even more important given this cohort’s normal baseline lung function and low mortality rates,” Goldfarb and colleagues wrote.

The risks for other cause-specific deaths were even higher, with each decrease linked to a 10% (HR = 1.1; 95% CI, 1.01-1.2) higher risk for heart disease-related mortality and a 26% (HR = 1.26; 95% CI, 1.1-1.44) higher risk for respiratory disease-related mortality.

Around 10% of the total cohort experienced FEV₁ drops of 64 mL or more per year. FEV₁ declines of 64 mL or more per year meant a heightened risk for all-cause death (HR = 2.91; 95% CI, 2.37-3.56) and cancer-cause death (HR = 2.68; 95% CI, 1.9-3.79) vs. a yearly decline of less than 64 mL.

The risk for death due to a heart disease (HR = 2.59; 95% CI, 1.63-4.12) or a respiratory disease (HR = 4.74; 95% CI, 2.2-10.24) also went up among those with an FEV₁ decline of 64 mL or more per year.

“Although aspects of the WTC exposure are unique, our study design could benefit the monitoring of other cohorts with occupational/environmental exposures,” Goldfarb and colleagues wrote. “Further research can test the hypothesis that chronic inflammation is a common cause of loss of lung function and increased mortality rates.”