Does Apolipoprotein ɛ4 interact with age or sex in cognitive function after traumatic brain injury?

Objective: The APOE ɛ4 allele has been associated poorer cognitive function following traumatic brain injury, however evidence to date has proven equivocal. The aim of this study was to investigate the impact of APOE ɛ4 on cognitive function following traumatic brain injury, and to explore the influence of age and sex on the impact of APOE ɛ4 versus the most common APOE allele; ɛ3.

Participants and Methods: Participants with traumatic brain injury were genotyped to determine APOE status and APOE ɛ4 and APOE ɛ3 carriers were assessed using a battery of cognitive tasks measuring executive function, working memory, and processing speed at 3, 6 and 12 months post-injury.

Results: Mixed modelling revealed that APOE ɛ4 carriers performed worse than the APOE ɛ3 group on only two of seven tasks (Trail Making Task B at 6 months, and the Controlled Oral Word Association Task), and therefore possession of APOE ɛ4 did not appear to systematically impair cognitive function. There was no evidence of interactions between age and APOE ɛ4, or sex and APOE ɛ4.

Conclusions: Our findings indicate that the APOE gene is unlikely to significantly impact on cognitive function following traumatic brain injury, and that neither age nor sex interact with APOE ɛ4 in this population. While the injury and demographic characteristics of our sample were reflective of the broader TBI population, further examination of these relationships in moderate to severe samples may be warranted.