Impact Of Cardiovascular Disease Risk Classification On The Stress Responses To Firefighting

Firefighters (FF) experience elevations in stress biomarkers during live-fire suppression, which is posited to exacerbate cardiovascular disease (CVD) risk. It is unclear if the occupational stress response differs between low-risk (LOW) and moderate-risk (MOD) FF classified by the American College of Sports Medicine (ACSM) standards. PURPOSE: This study assessed the differences in stress response to a live fire-training evolution (LFTE) between LOW and MOD CVD risk classification groups. METHODS: Forty-four (n = 44) FF completed an annual clinical health assessment, wherein they were risk-stratified in LOW or MOD classifications. Salivary samples were collected baseline (BL), immediately post (POST), and 30-min post the LFTE and analyzed for α-amylase (AA), secretory immunoglobulin-A (SIgA), and cortisol (CORT). Data were analyzed via a general linear model (GLM) analysis and percent mean changes from BL analysis. Data are shown as mean [UL, LL] and 95% confidence intervals (CIs). RESULTS: GLM analysis revealed an overall time effect (p < 0.001, ηₚ2 = 0.216) with no group x time effect (p = 0.796, ηₚ2 = 0.019) for the salivary stress biomarkers. Percent mean change from BL analysis revealed the MOD experienced clinically significant increases in CORT POST-LFTE (230.1% [60.8, 399.3], p = 0.009), while the LOW did not. The MOD and LOW experienced clinically significant increases in SIgA (LOW: 60.9% [23.4, 98.3], p = 0.002; MOD: 67.1% [24.2, 110.1], p = 0.003) and AA (LOW: 188.6% [98.6, 278.7], p < 0.001; MOD: 171.1% [67.8, 274.4], p = 0.002) POST-LFTE, and the MOD's AA concentrations remained elevated 30-min post-LFTE (127.1% [44.7, 209.4], p = 0.003). CONCLUSIONS: These data demonstrate that the MOD risk FF may experience greater stress levels during firefighting. While a healthier FF is more likely to handle the demanding occupational task requirements better than their unfit counterparts, future work should elucidate the impact of stress on CVD risk and occupational performance.