by Tom Valeo
Traumatic brain injury (TBI) increases the risk of dementia by 60 percent and accelerates onset by about two years, according to a study published in the June 25 online edition of Neurology.
However, the findings, based on medical records of 188,784 veterans with an average age of 68 when the study began, do not provide the fine-grained picture needed to differentiate the effects of milder from more severe TBIs, or the contributions from cardiovascular disease, diabetes, and other confounding factors for dementia, according to neurologists who analyzed the findings for Neurology Today.
Of the 1,229 vets diagnosed with a TBI, 196 (16 percent) developed dementia during the nine-year follow-up, compared with 18,255 (10 percent) who did not experience a TBI (adjusted hazard ratio, 1.57; 95% confidence interval: 1.35–1.83). And TBI victims who did not develop dementia died 2.3 years earlier than those not diagnosed with brain trauma.
Also, the authors, after adjusting for demographic factors and medical history, determined that risk of dementia increased among veterans with TBI if they also suffered from other risk factors such as depression, post-traumatic stress disorder (PTSD), or cerebrovascular disease.
The study helps to clarify conflicting evidence regarding the relationship between TBI and the risk of dementia, said the lead author Deborah E. Barnes, PhD, MPH, an associate professor of psychiatry and epidemiology and biostatistics at the University of California, San Francisco School of Medicine, and a researcher at the San Francisco Veterans Affairs Medical Center.
“Some studies have found an association, while others have found no association,” she said. “Our results come down on the side of head injury being associated with increased risk.”
Dr. Barnes acknowledged that the study did not distinguish different types of dementia. “For all-cause dementia, I think our findings are very strong, but we had limited power to look at dementia subtypes,” she said.
Also, the study relied on diagnoses made by clinicians, which could obscure the types of dementias acquired by the veterans. “We don’t know what criteria they used, so I have less confidence in the subtype data than I do in the all-cause dementia data,” she said.
A closer analysis of the medical records would yield more information about the severity and frequency of head trauma, “but it would be a time-intensive process,” Dr. Barnes said. “That is something we would like to do in the future, but it would be a massive undertaking, and we don’t have funding to do it now.”
An editorial in the same issue of Neurology praised the study for linking brain trauma to an increased risk of dementia, but also cited the need a more detailed analysis of the correlation.
Read the full discussion of these findings with commentary from outside experts in the August 7 issue of Neurology Today. See our previous coverage on the link between brain injury and dementia here: http://bit.ly/TBI-dmta.