Seasonal Changes In Cardiovascular Function, Risk Factors, And Oxidative Stress Of Wildland Firefighters

Abstract

Wildland firefighters (WLFF) experience extreme physiological strain throughout a typical season due to intense occupational demands and consistent woodsmoke exposure. There is a rationale to indicate that accumulated physiological strain, and oxidative stress, throughout a WLFF season has the potential to negatively alter cardiovascular function and risk factors. PURPOSE: The purpose of the study was to examine the effects of a season on cardiovascular function, risk factors, and markers of oxidative stress in WLFF. METHODS: Fourteen members of a Type I interagency hotshot crew participated in the study (males: n=13, females: n=1, age: 30.1 years ± 4.8). Pre- and post-seasonal resting measurements (May, October) were obtained for heart rate variability (lnRMSSD, lnHF, lnHF, LF:HF), pulse wave velocity (PWV), blood lipid panels (TC, TG, LDL, HDL), metabolic biomarkers (blood glucose, HbA1c), blood pressure (SBP, DBP) and blood oxidative stress (3-nitrotyrosine, 8-isoprostane). Paired samples t-tests were used to identify differences among pre- and post- seasonal values. RESULTS: There were no seasonal effects observed on resting heart rate variability, PWV, 3-nitrotyrosine, 8-isoprostane, TC, TG, LDL, blood glucose, SBP, or DBP (p>0.05). A significant reduction occurred in HDL (Pre: 53 mg/dL ± 14, Post: 45 mg/dL ± 18, p=0.043) and HbA1c increased (Pre: 5.2% ± 0.2, Post: 5.3% ± 0.2, p=0.034) from pre- to post-season. CONCLUSION: These data suggest a WLFF season did not impact resting markers of heart rate variability, pulse wave velocity, and oxidative stress. Alterations in metabolic biomarkers of cardiovascular risk factors (HDL and HbA1c) demonstrate unfavorable seasonal changes, suggesting that the WLFF season may increase cardiovascular risk.