Impact of Age on Non-Conventional Physiological Stress, Oxidative Stress, and Inflammatory Biomarkers Among First Responders

Previous studies have examined age-related CVD risk factors in small first-responder (FR) groups but haven't explored how age influences non-traditional stress markers and inflammation biomarkers. PURPOSE: To examine age-related differences in non-conventional physiological stress, oxidative stress, and inflammatory biomarkers among FRs. METHODS: Archival data for 170 FRs were analyzed from annual clinical testing. Age groups were 20-39 years and 40 years and above. General linear models (GLMs) were used to evaluate the effects of age group and occupational group on blood and salivary biomarkers: advanced oxidation protein products (AOPP), C-reactive protein (CRP), blood cortisol (CORT), salivary cortisol (sCORT), and salivary α-amylase (AA). Fisher’s Least Significant Difference tests and 95% upper and lower confidence intervals were used to assess pairwise comparisons of means and post-hoc tests. Partial Eta squared (ηp2) values were used to determine effect size. RESULTS: The GLM multivariate analysis revealed an overall Wilk's Lambda for the occupational group (p = 0.015, ηp2 = 0.117) with no statistically significant effect for the age group (p = 0.223, ηp2 = 0.060) nor age by occupational group (p = 0.868, ηp2 = 0.016). Univariate analysis showed a difference in C-reactive protein (p = 0.013, ηp2 = 0.052) by age group, while a difference in AOPP was noted by occupation (p = 0.022, ηp2 = 0.045). Pairwise comparisons revealed that older FRs (40 years and older) exhibited higher CRP concentrations than their younger FRs (0.062 mg/mL [0.013, 0.111], p = 0.013). Additionally, the firefighters exhibited higher AOPP concentrations than the law enforcement officers (35.747 µM [5.162, 66.333], p = 0.022). CONCLUSION: Age and occupation influence stress responses among FRs. Older personnel (≥40 years) showed increased inflammation (CRP), and firefighters had higher oxidative stress (AOPP) than law enforcement officers. Though age didn't affect all biomarkers, findings suggest cumulative effects of occupational exposure and aging on cardiometabolic and oxidative health. This highlights the need for ongoing monitoring and tailored wellness strategies.