J Korean Med Sci.  2021 Dec;36(50):e335. 10.3346/jkms.2021.36.e335.

Regional Gray Matter Volume Related to High Occupational Stress in Firefighters

• Lee D
• Kim W
• Lee JE
• Lee J
• Lee SK
• Chang SJ
• Jeung DY
• Hyun DS
• Ryu HY
• Kim C
• Jung YC

• KMID: 2523559
• DOI: http://doi.org/10.3346/jkms.2021.36.e335

Abstract

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.

Keyword

Firefighters; Neuropsychology; Stress; Gray Matter Volume

Figure

• 

  Fig. 1 Brain regions in which voxels had lower gray matter volume in the highly stressed group than the lowly stressed group. Statistical inference thresholds determined by uncorrected P values height threshold of 0.005, with an extent threshold of contiguous 10 voxels. Coordinates indicate locations of brain slices according to the Montreal Neurological Institute system. (A) Amygdala; (B) both sides of insula; (C) medial prefrontal cortex and anterior cingulate cortex.

• 

  Fig. 2 Correlation analysis of mean GMV values for clusters in the bilateral insula and the length of service for firefighters under high stress (n = 58). To depict partial correlation, we used linear regression to regress variables onto covariates. To generate scatter plots, we used calculated non-standardized residuals. (A) Smaller GMV in the left insula significantly correlated with longer years of service (r = −0.347, P = 0.009). (B) Smaller GMV in the right insula significantly correlated with longer years of service (r = −0.333, P = 0.012).GMV = gray matter volume.

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