Metabolic syndrome biomarkers have been validated as predictors of World Trade Center-related lung injury (WTC-LI) in a large population of exposed firefighters, according to a study published in CHEST.
This study included a baseline cohort of firefighters with normal forced expiratory volume in 1 second (FEV₁) before September 11, 2001 (9/11), who had been exposed to the WTC site (N=7487), and had serum tested prior to July 24, 2002. In longitudinal fashion, the participants were followed until August 1, 2017. Cases of WTC-LI were defined by FEV1 less than the lower limit of normal (LLN) at least twice during this time period. Diagnosis of metabolic syndrome was based on NCEP-ATP-III guidelines, with ≥3 criteria: systolic blood pressure (SBP) ≥130 mm Hg or diastolic blood pressure (DBP) ≥85 mm Hg, high density lipoprotein (HDL) <40 mg/dL, triglycerides ≥150 mg/dL, insulin resistance as glucose ≥100 mg/dL, or body mass index (BMI) >30 kg/m².
Metabolic syndrome-defined levels of triglycerides, HDL, SBP, DBP, and BMI were significant individual risk factors associated with developing WTC-LI. Having FEV₁<LLN at least twice was associated with high BMI, DBP, and triglycerides. A small but significant risk reduction of 1% for each additional year was associated with increasing age. Smoking increased the risk of WTC-LI by 15.2%. In addition, the most highly exposed individuals who were at the WTC site on the morning of 9/11 had 30.1% increase risk for WTC-LI vs an 18.7% increased risk if they arrived in the afternoon of 9/11 compared with the least exposed group.
Limitations of this study included insufficient data on cigarette smoking history (only self-reported smoking status), no pack-year history, and no secondhand smoke exposure data available.
To the authors’ knowledge, this was the first study to validate biomarkers of metabolic syndrome to predict WTC-LI, which is in contrast to other studies that suggest the opposite: possible lung injury predicts incident metabolic syndrome. This was also longest longitudinal study to demonstrate that metabolic syndrome risk factors may place patients at a higher risk for FEV1 loss than either particulate matter exposure or smoking.
Kwon S, Crowley G, Caraher EJ, et al. Validation of predictive metabolic syndrome biomarkers of World Trade Center lung injury: a 16-year longitudinal study [published online March 2, 2019]. CHEST. doi:10.1016/j.chest.2019.02.019