Apolipoprotein E (APOE) [epsilon]4 genotype is associated with reduced neuropsychological performance in military veterans with a history of mild traumatic brain injury

Introduction: The purpose of this study was to investigate the effect of the apolipoprotein E (APOE) [epsilon]4 allele on neuropsychological functioning in military Veterans with a remote history of mild traumatic brain injury (mTBI).Method: This cross-sectional study included 99 Veterans (mTBI = 53...

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Published in:Journal of clinical and experimental neuropsychology 2018-12, Vol.40 (10), p.1050
Main Authors: Merritt, Victoria C, Clark, Alexandra L, Sorg, Scott F, Evangelista, Nicole D, Werhane, Madeleine L, Bondi, Mark W, Schiehser, Dawn M, Delano-Wood, Lisa
Format: Article
Language:English
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Summary:Introduction: The purpose of this study was to investigate the effect of the apolipoprotein E (APOE) [epsilon]4 allele on neuropsychological functioning in military Veterans with a remote history of mild traumatic brain injury (mTBI).Method: This cross-sectional study included 99 Veterans (mTBI = 53; military controls, MC = 46) who underwent neuropsychological assessment and APOE genotyping. Three neurocognitive composite scores-memory (α = .84), speed (α = .85), and executive functioning (α = .76)-were computed from 24 norm-referenced variables, and the total number of impaired scores (>1.5 SDs below mean) for each participant was calculated.Results: Analyses of covariance adjusting for ethnicity and posttraumatic stress disorder (PTSD) symptoms revealed that although no significant differences were observed between mTBI [epsilon]4 allele groups on the executive functioning composite (p > .05), mTBI [epsilon]4+ Veterans performed more poorly than [epsilon]4- Veterans on the memory (p = .045, ηp2 = .083) and speed (p = .023, ηp2 = .106) composites. Furthermore, Mann-Whitney U tests showed that [epsilon]4+ mTBI Veterans displayed a significantly greater number of impaired scores than did [epsilon]4- mTBI Veterans (p = .010, r = .355). In contrast, there were no significant differences across any of the cognitive variables between [epsilon]4+ and [epsilon]4- MCs (all p > .05).Conclusions: Results suggest that APOE [epsilon]4 genotype is related to reduced memory and processingspeed performance, as well as overall cognitive impairment, in those with a history of mTBI, but does not appear to have the same negative effects on cognition in the absence of neurotrauma. Although results are preliminary, the present study advances understanding of genetic influences on cognitive functioning in Veterans with remote mTBIs. Future longitudinal work is needed to elucidate the underlying brain-based mechanisms of [epsilon]4 allelic effects on cognitive and clinical outcomes following TBI.
ISSN:1380-3395
1744-411X
DOI:10.1080/13803395.2018.1508555