title: Prevalence of Traumatic Brain Injury in Early Versus Late-Onset Alzheimer's Disease.
abstract: BACKGROUND
  Traumatic brain injury (TBI) is the most established environmental risk factor for Alzheimer's disease (AD), but it is unclear if TBI is specifically associated with early-onset AD (EOAD).
  
  
  OBJECTIVE
  To evaluate the relationship between TBI and EOAD (<65 years).
  
  
  METHODS
  We identified 1,449 EOAD, 4,337 late-onset AD (LOAD), and corresponding EOAD-matched and LOAD-matched normal controls (NC) in the National Alzheimer's Coordinating Center Uniform (NACC) database and compared the prevalence of any history of TBI as well as measures of cognition, function, behavior, and neuropathology. For validation, we determined TBI prevalence among 115 well-characterized clinic patients with EOAD.
  
  
  RESULTS
  Part A: The prevalence of any TBI in the NACC-database EOAD participants (13.3%) was comparable to that observed in the clinic EOAD patients (13.9%) but significantly higher than in the NACC-database LOAD participants (7.7% ; p <  0.0001) and trended to higher compared to EOAD-matched NC (11.1% ; logistic regression p = 0.053). Part B: When we compared EOAD patients with documented non-acute and non-residually impairing TBI to EOAD without a documented history of prior TBI, those with TBI had significantly more disinhibition. Part C: Autopsies did not reveal differences in AD neuropathology based on a history of TBI.
  
  
  CONCLUSIONS
  These findings suggest, but do not establish, that TBI is a specific risk factor for EOAD and may lead to disinhibition, a feature that often results from the frontal effects of head injury. This study recommends further research on the effects of TBI in EOAD in larger numbers of participants.
authors.affiliation: Department of Neurology, University of California Los Angeles (UCLA), Los Angeles, CA, USA.|David Geffen School of Medicine, University of California Los Angeles (UCLA), Los Angeles, CA, USA.|Department of Neurology, Neurobehavior Unit, V.A. Greater Los Angeles Healthcare System, Los Angeles, CA, USA.
authors.forename: Mario F
authors.initials: MF
authors.lastname: Mendez
authors.affiliation: Department of Neurology, University of California Los Angeles (UCLA), Los Angeles, CA, USA.|David Geffen School of Medicine, University of California Los Angeles (UCLA), Los Angeles, CA, USA.|Department of Neurology, Neurobehavior Unit, V.A. Greater Los Angeles Healthcare System, Los Angeles, CA, USA.
authors.forename: Pongsatorn
authors.initials: P
authors.lastname: Paholpak
authors.affiliation: Department of Neurology, University of California Los Angeles (UCLA), Los Angeles, CA, USA.|David Geffen School of Medicine, University of California Los Angeles (UCLA), Los Angeles, CA, USA.|Department of Neurology, Neurobehavior Unit, V.A. Greater Los Angeles Healthcare System, Los Angeles, CA, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Lin
authors.affiliation: David Geffen School of Medicine, University of California Los Angeles (UCLA), Los Angeles, CA, USA.
authors.forename: Jeannie Y
authors.initials: JY
authors.lastname: Zhang
authors.affiliation: Department of Neurology, University of California Los Angeles (UCLA), Los Angeles, CA, USA.|David Geffen School of Medicine, University of California Los Angeles (UCLA), Los Angeles, CA, USA.|Department of Neurology, Neurobehavior Unit, V.A. Greater Los Angeles Healthcare System, Los Angeles, CA, USA.
authors.forename: Edmond
authors.initials: E
authors.lastname: Teng
mesh_terms: D017668:Age of Onset; D000544:Alzheimer Disease / Q000150:complications / Q000453:epidemiology* / Q000523:psychology; D001930:Brain Injuries / Q000150:complications / Q000453:epidemiology* / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D015995:Prevalence; D012307:Risk Factors; D014481:United States / Q000453:epidemiology
keywords: Aging; Alzheimer’s disease; concussion; dementia; epidemiology; head injury; memory loss; neurodegeneration; risk factors; traumatic brain injury