1. A history of mild traumatic brain injury (TBI) in healthy, middle-aged adults was associated with detectable changes in neuroimaging and clinical outcomes such as poorer sleep and depressive symptoms.

Evidence Rating Level: 2 (Good)

Study Rundown: While TBI has been recognized as a risk factor for dementia, the precise mechanisms linking the two processes are not well understood. Vascular injury, such as cerebral microbleeds (CMB), is a common pathology that arises from TBI. However, the influence of TBI history on the associations between CMB and vascular risk factors and observable clinical deficits has not been well established. This study therefore sought to investigate the association between TBI history and observable neuroimaging and clinical features in middle-aged adults.

In this cross-sectional study, 617 participants between 40 and 59 years of age with no existing cognitive impairments were assessed for CMB and imaging markers of small vessel disease (SVD) via 3T MRI. Cognitive performance, TBI history and cardiovascular disease (CVD) risk were each assessed. CMB were not found to be related to CVD risk, but were associated with history of TBI. Greater number of TBI events was also associated with clinical deficits such as poorer sleep, gait disturbances and increased depressive symptoms.

Overall, this study found that a history of TBI was associated with detectable changes in brain imaging as early as midlife in otherwise healthy adults, supporting the mechanism of vascular injury as a possible link between TBI and neurodegenerative processes.

Click to read the study in JAMA Network Open

Relevant Reading: Traumatic microbleeds suggest vascular injury and predict disability in traumatic brain injury

In-Depth [cross-sectional study]: While TBI has been recognized as a risk factor for dementia, the pathophysiological mechanisms connecting the two processes are not well understood. Vascular injury is a common pathology that arises from TBI, with cerebral microbleeds (CMB) representing a possible consequence of TBI and a marker for cerebral small vessel disease (SVD). However, TBI has rarely been considered as a cause of CMB in the study of SVD, leading to inconsistencies in the association between CMB and other established correlates of SVD such as vascular risk factors including hypertension. This study therefore sought to investigate the association between lifetime TBI history and early SVD, as well as TBI history and CMB and other measurable vascular risk factors.

617 participants (median [IQR] age, 52 [47-56] years) between 40 and 59 years of age and cognitively healthy were assessed for CMB and imaging markers of SVD via 3T MRI. Cognitive performance was assessed using the Computerized Assessment of Information Processing (COGNITO) battery. TBI history and cardiovascular disease (CVD) risk were also assessed using the Brain Injury Screening Questionnaire (BISQ) and the Framingham Risk Score respectively. CMB were found to be associated with greater age (β = 0.07; 95% CI, 0.03-0.11) but were not related to CVD risk. CMB were greater in individuals with a history of TBI compared to participants without TBI history, with an observed dose-response association between CMB and increasing number of TBI events (95% CI, 0.01-0.09). In interaction analyses, the association between CMB and greater CVD risk was found to be lower with increasing number of TBI events. History of TBI events was also associated with clinical deficits including worse sleep quality and greater depressive symptoms, but not cognition.

Image: PD

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