Widespread cortical morphological alterations are associated with repetitive blast exposure independent of concussion history

BackgroundConcussion is a public health crisis, but mounting evidence indicates that repetitive subconcussive head impacts can also lead to lasting structural and functional brain changes. Subconcussive exposures are common in military environments where personnel are routinely subjected to occupational blast overpressure. While functional consequences of blast exposure are increasingly recognized, corresponding structural alterations remain less consistently reported. Here, we investigated how cumulative subconcussive exposure relates to cortical and subcortical brain structure in a military cohort. MethodsUsing FreeSurfer, we analyzed high-resolution T1-weighted images from 80 participants (n = 41 high blast, n = 39 low blast; 4 and 8 females, respectively), grouped by lifetime blast exposure history using the generalized blast exposure value. Vertex-wise general linear models tested for cortical differences in cortical volume, thickness, surface area, and curvature, adjusting for age, trauma exposure, and diagnosed concussion count. ANCOVAs evaluated subcortical volume differences. ResultsCompared to the low blast group, individuals with high blast exposure demonstrated widespread cortical alterations. Across metrics, higher values were predominantly observed in frontal and central regions, including the precentral and superior frontal gyri, whereas lower metrics mainly appeared in temporal, parietal, and occipital cortices. Specifically, high blast participants showed greater cortical volume, thickness, and surface area in precentral and superior frontal regions, higher curvature in frontoparietal and temporal areas, and reduced volume, surface area, and thickness in lateral temporal, parietal, and occipital cortices (e.g., supramarginal, inferior parietal, and lingual gyri) and the entorhinal cortex. Subcortically, high blast participants showed no volumetric differences from the low blast group. ConclusionThese findings provide evidence that repetitive subconcussive blast exposure alters cortical morphometry, independent of concussion history, suggesting complex, spatially heterogenous structural changes and highlighting the need for proactive monitoring and mitigation strategies in operational populations.