Chronic inflammation after severe traumatic brain injury: Characterization and associations with outcome at 6 and 12 months postinjury

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Study examined associations between chronic inflammatory profiles and outcome 6 to 12 months following severe traumatic brain injury (TBI). Blood was collected in 2-week intervals from 87 adults with severe TBI and 7 healthy controls. Serum cytokines (interleukin [IL]-1β, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, tumor necrosis factor α) were measured at 2 weeks to 3 months, 4- to 6-month averages, and 6- and 12-month levels. The primary outcomes were 6- and 12-month Glasgow Outcome Scale (GOS) scores. Serum levels of IL-1β, IL-6, IL-8, IL-10, and tumor necrosis factor α were elevated over 3 months following TBI. Multivariate analysis showed that increased cytokine load score was associated with a 1.21 and 1.18 (increase in odds of unfavorable GOS score at 6 and 12 months, respectively. Also, elevated IL-6/IL-10 ratios were associated with increased odds of unfavorable outcomes at 6 months (adjusted odds ratio = 1.76). Findings suggest that TBI can be viewed as a condition with a persistent inflammatory state. The subacute cytokine load score classifies individuals at risk for unfavorable outcomes following injury. Higher proinflammatory burden with IL-6, relative to the anti-inflammatory marker IL-10, is significantly associated with outcome. Further research should examine whether inflammatory genes and other inflammatory biomarkers affect risk for unfavorable outcomes and TBI complications.

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