Is traumatic brain injury associated with late-life neurodegenerative conditions?

Traumatic brain injury (TBI) with loss of consciousness was not associated with late-life mild cognitive impairment, Alzheimer disease or dementia but it appeared to be associated with increased risk for other neurodegenerative and neuropathologic findings, according to a new article published online by JAMA Neurology.

Most TBIs are mild and most people return to their prior level of functioning. Still, concern over late-life effects of TBIs has grown with increased awareness of repetitive head trauma in athletes and head injuries suffered by service members in military conflicts. But most TBIs are not sports related or caused by combat injuries so understanding late-life effects in nonathlete civilians is important.

Paul K. Crane, M.D., M.P.H., of the University of Washington, Seattle, and coauthors analyzed data from 7,130 participants in three other studies, including older religious clergy, older residents from Chicago-area retirement homes and subsidized housing, and older Seattle-area Group Health members. The average age of participants was nearly 80 and 865 reported a history of TBI with loss of consciousness (LOC).

Although 1,537 cases of dementia and 117 cases of Parkinson disease (PD) were identified in follow-up, the authors reported no association was found between TBI with LOC and dementia or Alzheimer disease (AD). Authors did, however, report associations between TBI with LOC and increased risk for PD, progression of parkinsonism, Lewy body accumulation and microinfarcts, which are small strokes.

Study limitations include that data from participants may not be broadly representative of the ethnically diverse U.S. population and other mitigating factors may have affected the findings.

"Traumatic brain injury with LOC sustained early in life is not innocuous and appears to be associated with neurodegenerative conditions, although not AD," the article concludes.