Repetitive traumatic brain injuries (TBIs) among military personnel have been linked to chronic behavioral and neurological symptoms, and poor health outcomes. Repetitive TBIs may impact inflammation, which may offer some explanation of the biological basis of these long-term risks, and may improve the care that is provided to these individuals. This study examines the concentrations of TNFα, IL-6 and IL-10 and associations with behavioral symptoms, including post-traumatic stress disorder symptoms and depression in a cohort of 106 military personnel and Veterans with a history of TBI. Group comparisons conducted for those with repetitive TBIs (> 3; n = 44), to participants with less than three TBIs (n = 29), and controls with no TBIs (n = 33). The primary outcomes were serum levels of inflammatory related proteins TNF-α, IL-6 and IL-10, TBI history, and PTSD symptoms. IL-6 mean concentration was significantly higher in the repetitive TBI group compared to those with 1-2 TBI or no TBI history (p = 0.050). Additionally, for participants with a history of TBI, PTSD symptom severity, specifically, intrusion (p = .006 and p = .007) and avoidance (p = .034 and .009), were significant predictors of higher IL-6 and IL-10 concentrations respectively. These findings suggest that repetitive TBIs concurrent with high PTSD symptoms in military personnel and Veterans are associated with chronic inflammation, and specifically elevated concentrations of IL-6. Examining the changes in inflammatory processes may identify potential therapeutic targets for early intervention after TBI in order to prevent the development of neurological deficits and disorders.
Keywords: Cytokines; Inflammation; Military; Post-traumatic stress disorder (PTSD); Traumatic brain injury (TBI); interleukin-6 (IL-6).
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