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 2005 participants (mean age: 47.6 years, standard deviation: 5.0, women: 65%) from the Origins of Alzheimer's Disease Across the Life Course (ORACLE) study between 2017 and 2020. History of traumatic brain injury was defined as at least one lifetime self-reported brain 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 lobe volume, gray matter volume, white matter volume, white matter hyperintensities volume, infarcts, and microbleeds, measured with brain magnetic resonance imaging [MRI]) were assessed using linear or logistical regression models and adjusted for relevant confounders. In total, 250 of 2005 (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 had occurred >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 >10 years ago (OR:1.69; 95% CI: 1.15, 2.50). Additionally, the association was stronger in those with >30 min loss of consciousness (OR: 3.57; 95% CI: 1.48, 8.59) than in those with <30 min loss of consciousness (OR: 1.85; 95% CI: 1.25, 2.74), when compared with 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 lifetime 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.