Research Reports - Traumatic brain injury history is associated with earlier age of onset of Alzheimer disease
Clin Neuropsychol. 2016 Nov 18:1-14. [Epub ahead of print]
LoBue C(1), Wadsworth H(1), Wilmoth K(1), Clem M(1), Hart J Jr(1,)(2,)(3), Womack
KB(1,)(2,)(3), Didehbani N(1,)(3), Lacritz LH(1,)(2), Rossetti HC(1), Cullum
OBJECTIVE: This study examined whether a history of traumatic brain injury (TBI)
is associated with earlier onset of Alzheimer disease (AD), independent of
apolipoprotein ε4 status (Apoe4) and gender.
METHOD: Participants with a clinical diagnosis of AD (n = 7625) were obtained
from the National Alzheimer's Coordinating Center Uniform Data Set, and
categorized based on self-reported lifetime TBI with loss of consciousness (LOC)
(TBI+ vs. TBI-) and presence of Apoe4. ANCOVAs, controlling for gender, race, and
education were used to examine the association between history of TBI, presence
of Apoe4, and an interaction of both risk factors on estimated age of AD onset.
RESULTS: Estimated AD onset differed by TBI history and Apoe4 independently
(p's < .001). The TBI+ group had a mean age of onset 2.5 years earlier than the
TBI- group. Likewise, Apoe4 carriers had a mean age of onset 2.3 years earlier
than non-carriers. While the interaction was non-significant (p = .34),
participants having both a history of TBI and Apoe4 had the earliest mean age of
onset compared to those with a TBI history or Apoe4 alone (MDifference = 2.8 and
2.7 years, respectively). These results remained unchanged when stratified by
CONCLUSIONS: History of self-reported TBI can be associated with an earlier onset
of AD-related cognitive decline, regardless of Apoe4 status and gender. TBI may
be related to an underlying neurodegenerative process in AD, but the implications
of age at time of injury, severity, and repetitive injuries remain unclear.