Apolipoprotein E and traumatic brain injury in a military population: evidence of a neuropsychological compensatory mechanism?
- S Duke Han1,
- Angela I Drake2,
- Lynne M Cessante2,
- Amy J Jak3,
- Wes S Houston4,
- Dean C Delis5,
- J Vincent Filoteo5,
- Mark W Bondi5
- 1 Department of Psychology, Loyola University Chicago, Chicago, Illinois, USA
- 2 Defense and Veterans Brain Injury Center, Neurosciences Department, Naval, Medical Center San Diego, San Diego, California, USA
- 3 Veterans Medical Research Foundation, San Diego, California, USA
- 4 Department of Neurology, University of Iowa, Iowa City, Iowa, USA
- 5 Department of Psychiatry, University of California San Diego School of Medicine, San Diego and Psychology Service, VA San Diego Healthcare System, San Diego, California, USA
- Dr Mark W Bondi, VA San Diego Healthcare System (116B), 3350 La Jolla Village Drive, San Diego, CA 92161, USA; mbondi{at}ucsd.edu
- Received 3 October 2006
- Revised 19 January 2007
- Accepted 22 January 2007
- Published Online First 7 February 2007
Abstract
Objective: Although research has implicated the apolipoprotein E (APOE) epsilon-4 genotype as having a negative effect on neuropsychological outcomes following traumatic brain injury (TBI), the potentially negative role of the ϵ4 allele on TBI outcomes has recently been challenged. In light of this debate, the present study served to examine the role of APOE genotype on neuropsychological outcomes approximately 1 month following mild to moderate TBI in a military population. Because of the well documented role of the APOE-ϵ4 allele in increasing the risk of Alzheimer’s disease, we predicted that persons with the APOE-ϵ4 genotype would display relatively greater deficits in cognition than their non-ϵ4 counterparts.
Methods: 78 participants were consecutively recruited following a mild to moderate TBI and were divided into two groups based on the presence or absence of an APOE ϵ4 allele. Groups were comparable on demographic characteristics and psychosocial outcomes. Participants were administered a comprehensive neuropsychological battery.
Results: Analyses revealed comparable performances on most neuropsychological measures and better performances by ϵ4 carriers on select measures of attention, executive functioning and episodic memory encoding. Furthermore, differences remained after accounting for the effects of TBI severity.
Conclusions: Evidence from these analyses supports current literature refuting the notion of relatively poorer neuropsychological functioning associated with the APOE-ϵ4 genotype among young adult participants shortly following mild or moderate brain injury. Neuropsychological performance differences by APOE genotype following TBI are discussed in terms of the importance of considering severity of injury, timing of postinjury assessment and possible neurocognitive compensatory mechanisms.
Footnotes
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Competing interests: Dr Delis is a co-author of the D-KEFS (Delis–Kaplan Executive Functions System) and receives royalties from the test. There were no other actual or potential conflicts of interest for the authors that could have inappropriately influenced the present work. Subjects were recruited in accordance with Internal Review Board (IRB) approved policies and procedures. Standard professional and ethical guidelines were upheld during the research study and manuscript preparation. The views expressed in this article do not necessarily reflect those of the funding agency, the United States Navy, the United States Marine Corps, the Department of Defense or the United States Government.
- Abbreviations:
- AD
- Alzheimer’s disease
- APOE
- apolipoprotein E
- CVLT-II
- California Verbal Learning Test-second edition
- D-KEFS
- Delis–Kaplan Executive Functions System
- DVBIC
- Defense and Veterans Brain Injury Center
- GOS
- Glasgow Outcome Scale
- TBI
- traumatic brain injury
- WAIS-III
- Wechsler Adult Intelligence Scale-third edition
- WMS-III
- Wechsler Memory Scale-third edition
