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History of traumatic brain injury in relation to cognitive functioning, memory complaints and brain structure in mid-life.

In this study, we investigated history of traumatic brain injury with loss of consciousness in relation to cognitive functioning, subjective memory complaints and brain structure in mid-life. This study included 2,005 participants (mean age: 47.6 years, standard deviation: 5.0, women: 65%) from the ORACLE study between 2017-2020. History of traumatic brain injury was defined as at least one life-time self-reported head injury with loss of consciousness. Associations of history of traumatic brain injury with (1) cognitive functioning (measured with the 15-Word learning test, Stroop task, Letter-digit substitution test, Word fluency test, Purdue pegboard test, and Design organization test) (2) current subjective memory complaints (present/absent, measured with a survey), and (3) brain structure (total brain volume, frontal and temporal lobes volume, gray matter volume, white matter volume, white matter hyperintensities volume, infarcts, and microbleeds, measured with brain-MRI) were assessed using linear or logistic regression models and adjusted for relevant confounders. In total, 250 of 2,005 (12%) participants reported a history of traumatic brain injury. Of those who reported the time post-injury (n=173), most participants (n=151, 87%) reported that it occurred more than 10 years ago. We found no associations between history of traumatic brain injury and any of the cognitive tests. We did find that a history of traumatic brain injury was associated with having mid-life subjective memory complaints (odds ratio (OR): 1.87, 95% confidence interval (CI): 1.35; 2.58). This association was also present when investigating only those who reported an injury more than 10 years ago (OR:1.69, 95% CI: 1.15; 2.50). Additionally, the association was stronger in those with more than 30 minutes loss of consciousness (OR: 3.57, 95%CI: 1.48; 8.59) than in those with less than 30 minutes loss of consciousness (OR: 1.85, 95%CI: 1.25; 2.74), when compared to those without history of traumatic brain injury. Lastly, we found no associations between history of traumatic brain injury and any of the structural brain-MRI outcomes. In conclusion, our study suggests that at least one life-time traumatic brain injury with loss of consciousness in mid-life is associated with long-term subjective memory complaints, but not with cognitive functioning or brain structure.