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Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Firefighters are exposed to physical and mental threats in the working environment that put them at risk for occupational stress and burnout. Stress responses can impact the functional interactions between brain regions involved in emotional and cognitive regulation. The objective of this study was to investigate brain functional connectivity (FC) related to occupational stress in firefighters. Male firefighters (n = 77) completed the Korean Occupational Stress Scale questionnaire on occupational stress and underwent brain magnetic resonance imaging. Seed-based FC analyses were conducted by setting core regions of the large-scale functional networks as seeds. Subsequent correlational analyses detected relationships between occupational stress scale scores and brain FC. The results showed that occupational stress was negatively correlated with FC between the central executive network (CEN)-related brain regions and seed regions of other networks. Additionally, occupational stress was negatively correlated with FC within the default mode network (DMN), but positively correlated with FC between the salience network (SN) and the DMN. Changes in FC in large-scale neural networks are likely involved in occupational stress responses. Taken together, these results suggest that proper management of occupational stress may help prevent the occurrence of clinical problems caused by changes in brain functional networks., (Copyright © 2022. Published by Elsevier B.V.)

Background: Firefighters inevitably encounter emotionally and physically stressful situations at work. Even firefighters without diagnosed post-traumatic stress disorder receive clinical attention because the nature of the profession exposes them to repetitive trauma and high occupational stress. This study investigated gray matter abnormalities related to high occupational stress in firefighters using voxel-based morphometry (VBM) and surface-based morphometry (SBM)., Methods: We assessed 115 subjects (112 males and 3 females) using magnetic resonance imaging and evaluated occupational stress by the Korean Occupational Stress Scale-26 (KOSS-26). Subjects were classified into highly or lowly stressed groups based on the median value of the KOSS-26., Results: In VBM analysis, we found that firefighters with high occupational stress had lower gray matter volume (GMV) in both sides of the insula, the left amygdala, the right medial prefrontal cortex (mPFC), and the anterior cingulate cortex than firefighters with low occupational stress. In SBM analysis based on regions of interest, the GMV of the bilateral insula and right mPFC were also lower in the highly stressed group. Within the highly stressed group, low GMV of the insula was significantly correlated with the length of service (left: r = -0.347, P = 0.009; right: r = -0.333, P = 0.012)., Conclusion: Our findings suggest that regional GMV abnormalities are related to occupational stress. Regional gray matter abnormalities and related emotional dysregulation may contribute to firefighter susceptibility to burnout., Competing Interests: The authors have no potential conflicts of interest to disclose., (© 2021 The Korean Academy of Medical Sciences.)

Background: Alcohol, a known addictive substance, affects the structural properties of the brain. In this study, we explored associations between alcohol use and gray matter properties among firefighters, who are often exposed to significant occupational stress., Methods: Gray matter volume (GMV) was evaluated using voxel-based morphometry in 287 male firefighters (mean age: 48.8 ± 7.7 years). Firefighters were classified into 32 never-drinkers, 162 non-heavy alcohol users, and 93 heavy alcohol users according to their alcohol consumption. GMV was compared between groups, and the correlations between GMV and alcohol use were investigated. A voxel-wise height threshold of p < 0.001 (uncorrected) was used, with small volume correction applied on cluster level., Results: Heavy alcohol users had lower GMV in the bilateral thalamus than non-heavy alcohol users or never-drinkers. Heavy alcohol users also showed lower GMV in the left insula, compared to other groups. The higher the alcohol consumption among firefighters, the lower the GMV of the right thalamus., Conclusions: The results of this study show that heavy alcohol use has an association with lower GMV in several core regions, including the thalamus. When considering the impact of these brain regions on cognitive and behavioral control, our findings suggest a need for concern about heavy alcohol use among firefighters., (Copyright © 2021. Published by Elsevier B.V.)