Traumatic Brain Injury Linked to Early Age Dementia

by | Sep 3, 2019 | 2018, Alzheimer's Disease, Brain Health, Cognitive Health

Written by Joyce Smith, BS. Using autopsy-confirmed diagnosis, researchers found that a history of traumatic brain injury with reported loss of consciousness is a risk factor for earlier onset of Alzheimer’s disease.

Alzheimer's - Brain healthTraumatic brain injury severity (TBI), age at injury, and repeated injuries may be factors that increase the risk for later development of cognitive decline 1 dementia, and Alzheimer’s disease (AD) 2-4. However, not all studies support an association 5. There is evidence that TBI may contribute to the accumulation of amyloid-beta (Aß) plaques, neurofibrillary tangles (NFTs) and Lewy bodies 6, which are the hallmark of AD pathology; yet, establishing a causal link to dementia has been difficult to prove. One study found that individuals diagnosed with AD, cognitive impairment and dementia and who had a past history of TBI (greater than one year prior to evaluation) and with reported loss of consciousness (LOC) had an approximately 2.5 earlier age onset for each condition 3. Other studies have found no association between TBI and early age onset 7.

To further explore a potential link and add clarity to TBI as a risk factor for earlier onset of AD, Schaffert and team 8 investigated cases of AD as confirmed by autopsy findings and how they relate to a history of head injuries. They examined data from the National Alzheimer’s Coordinating Center (NACC) Uniform Data Sets (UDS) and Neuropathology Data Set (NDS), both of which collect clinical, autopsy, demographic, and genetic data on people diagnosed with AD or other brain pathologies.

  • Of the 2,153 study participants with autopsy-confirmed AD, 197 reported history of TBI with LOC (TBI+) while 1,956 had no history of repeated head injuries (TBI-). The combined TBI+ and TBI- groups consisted of well-educated participants who were 94% Caucasian.
  • Average age of dementia onset was 2.34 years earlier (p = 0.01) for the TBI+ group (n = 194) versus the TBI− group (n = 1900).
  • Dementia was diagnosed on average 2.83 years earlier (p = 0.002) in the TBI+ group (n = 197) versus the TBI− group (n = 1936).
  • Among those with the highest probability of dementia due to AD, age of symptom onset and age of diagnosis occurred 3.6 years earlier (both p’s < 0.001) in the TBI+ group compared to the TBI- group. These results were determined using more stringent neuropathological criteria (i.e., Braak stages V–VI and CERAD frequent).
  • Even when controlling for confounding factors such as lifetime history of depression, family history of dementia, education level, and medical history, the link between dementia and TBI remained strong.

Study limitations included the use of a national registry consisting of predominantly well-educated Caucasians, which could limit generalizability. The database did not capture TBI severity or frequency or account for post traumatic amnesia which could disguise as a brief loss of consciousness (LOC). In spite of these limitations the authors believe this is the first study to find that a history of TBI with reported LOC occurring more than one year prior to diagnosis  was associated with an approximately 3-year  earlier age symptom onset and diagnosis  in individuals with autopsy -confirmed AD. This was consistent with a previous study that used clinical rather than autopsy diagnoses 3.

The authors believe this study adds to the growing body of evidence that a traumatic brain injury (TBI) with loss of consciousness (LOC) is a risk factor for developing Alzheimer’s-related dementia earlier than someone without a history of TBI without LOC 9. Future research is needed to understand what specific injury and demographic characteristics may put some individuals more at risk than others, and the mechanism by which TBI may accelerate the onset of these disorders.

Source: Schaffert, Jeff, Christian LoBue, Charles L. White III, Hsueh-Sheng Chiang, Nyaz Didehbani, Laura Lacritz, Heidi Rossetti, Marisara Dieppa, John Hart Jr, and C. Munro Cullum. “Traumatic brain injury history is associated with an earlier age of dementia onset in autopsy-confirmed Alzheimer’s disease.” (2018).

Posted September 3, 2019.

Joyce Smith, BS, is a degreed laboratory technologist. She received her bachelor of arts with a major in Chemistry and a minor in Biology from  the University of Saskatchewan and her internship through the University of Saskatchewan College of Medicine and the Royal University Hospital in Saskatoon, Saskatchewan. She currently resides in Bloomingdale, IL.

References:

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  2. LoBue C, Denney D, Hynan LS, et al. Self-Reported Traumatic Brain Injury and Mild Cognitive Impairment: Increased Risk and Earlier Age of Diagnosis. Journal of Alzheimer’s disease : JAD. 2016;51(3):727-736.
  3. LoBue C, Wadsworth H, Wilmoth K, et al. Traumatic brain injury history is associated with earlier age of onset of Alzheimer disease. The Clinical neuropsychologist. 2017;31(1):85-98.
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  9. Ruff RM, Iverson GL, Barth JT, Bush SS, Broshek DK. Recommendations for diagnosing a mild traumatic brain injury: a National Academy of Neuropsychology education paper. Archives of clinical neuropsychology : the official journal of the National Academy of Neuropsychologists. 2009;24(1):3-10.