ABSTRACT
OBJECTIVE: Older adults (OA) after mild traumatic brain injury (mTBI) have a high risk of developing persistent post-injury cognitive impairments. Lower pre-morbid cognitive reserve (CR) is increasingly investigated as a risk factor for cognitive dysfunction in OA. However, how CR protects against effects of mTBI at the brain level remains largely understudied. METHODS: We examined 22 OA who sustained mTBI (mean 67.69 years, SD 5.11) in the sub-acute phase and 15 age- and CR-matched healthy OA (mean 68 years, SD 5.55) performing a three-level visual N-back task using electroencephalography. We calculated inverse efficiency scores of performance from accuracy and reaction times. Event-related potentials served as neurocognitive correlates of attentional (P2) and working memory (P3) processing. RESULTS: Overall, mTBI OA performed worse than healthy OA (p = 0.031). Lower CR generally decreased performance (p < 0.001). Furthermore, with increasing task difficulty, task performance was more affected by CR (p = 0.004). At the brain level, P2 amplitude was lower in mTBI OA than in healthy OA (p = 0.05). There was no clear effect of CR on P2 or P3 measures. CONCLUSION: As mTBI OA with lower CR performed worse on a working-memory task, lower CR may be a risk factor for worse recovery after mTBI in this group.
