Impact of aging on the immune response to traumatic brain injury (AIm:TBI) study protocol

Traumatic brain injury (TBI) in older adults leads to considerable morbidity and mortality. Outcomes among older adults with TBI are disparately worse than in younger adults. Differences in immunological response to injury may account for at least some of this disparity. Understanding how ageing differentially affects the immune response to TBI and how older age and these immunological changes affect the natural history of recovery following TBI are the goals of this study.

A prospective multiple cohort design is being used to assess the effects of ageing and TBI on immune makers and to test predictors of impairment and disability in older adults following mild TBI. Older adults (>55 years) with mild TBI are enrolled with three comparison groups: younger adults (21-54 years) with mild TBI, non-injured older adults (>55 years) and non-injured young adults (21-54 years). For the primary analysis, we will assess the association between immune markers and Glasgow Outcome Scale-Extended at 6 months, using logistic regression. Predictors of interest will be inflammatory biomarkers. Multivariate linear regression will be used to evaluate associations between biomarkers and other outcomes (symptoms, function and quality of life) at 3 and 6 months. Exploratory analyses will investigate the utility of biomarkers to predict outcome using receiver-operating characteristic curves.

A better understanding of the recovery trajectory and biological rationale for disparate outcomes following TBI in older adults could allow for development of specific interventions aimed at reducing or eliminating symptoms. Such interventions could reduce impairment and healthcare costs.