Association between occupational stress exposure and altered white matter integrity in firefighters

Background Firefighters experience chronic occupational stress due to frequent trauma exposure and shift work, which contributes to stress-related symptoms such as sleep disturbance and somatic complaints. Despite a few neuroimaging studies in this population, white matter (WM) integrity and its clinical implications remain insufficiently understood. We investigated WM microstructural alterations in firefighters and explored their associations with occupational stress and related symptoms. Methods Ninety-four firefighters and 98 healthy non-firefighter controls underwent diffusion tensor imaging (DTI) and completed standardized clinical assessments. Tract-based spatial statistics (TBSS) was applied to assess voxel-wise group differences in four representative diffusion indices. Associations between altered diffusion characteristics and cumulative emergency duty exposure and stress-related symptoms, including sleep quality and somatic symptoms, were evaluated. Results Firefighters exhibited a widespread increase in axial diffusivity (AD) across the parietal, frontal, limbic, brainstem, and cerebellar regions, with elevated mean diffusivity (MD) in overlapping but less extensive areas, compared to non-firefighter controls (corrected- p < 0.05). Among firefighters, greater cumulative emergency duty exposure was significantly associated with higher AD (β = 0.30, p = 0.014) and MD (β = 0.29, p = 0.016) within regions showing group differences. Furthermore, higher AD was correlated with poorer sleep quality (β = 0.24, p = 0.015) and more severe somatic symptoms (β = 0.19, p = 0.040). Conclusions Chronic occupational stress in firefighters is associated with widespread WM microstructural alterations, which in turn correlate with poorer sleep quality and increased somatic symptoms. These findings suggest a neurobiological pathway linking occupational stress to clinical outcomes and underscore the need for early detection and targeted interventions in the high-risk occupational group.