White veterans at greatest risk for dementia diagnoses following TBI

A study of U.S. Veterans Health Administration (VHA) data found race- and sex-based differences in the relationship between traumatic brain injury (TBI) and all-cause dementia diagnoses.

“All race groups with TBI had increased risk of dementia diagnosis, but there was an interaction effect such that white veterans were at greatest risk for dementia following TBI,” reported Erica Kornblith PhD, of the San Francisco Veterans Affairs Health Care System, and coauthors.

“Further research is needed to understand mechanisms for this discrepancy,” they wrote in Neurology. “Differences in dementia diagnosis risk for males and females after TBI were significant but small, and male and female veterans had similarly high risk of dementia diagnosis after TBI.”

Adjusted hazard ratios by racial group for any dementia diagnosis for veterans with TBI, compared with veterans who did not have TBI, were:

  • White: HR 2.93, 95% CI 2.86-3.00.
  • Black: HR 2.27, 95% CI 2.13-2.41.
  • Hispanic: HR 1.98, 95% CI 1.74-2.24.

Of individuals with TBI, white veterans had a higher risk of being diagnosed with dementia compared with Black and Hispanic veterans, with adjusted HRs of:

  • White: HR 2.71, 95% CI 2.64-2.77.
  • Black: HR 2.15, 95% CI 2.02-2.30.
  • Hispanic: HR 1.74, 95% CI 1.51-2.01.

Sensitivity analysis for number of clinic visits (more medical attention might change diagnosis rates) and a 1-year “washout” analysis slightly attenuated risk estimates, but the pattern remained.

In an accompanying editorial, Andrea Schneider, MD, PhD, of the University of Pennsylvania in Philadelphia, and Kristen Dams-O’Connor, PhD, of the Icahn School of Medicine in New York City, wrote, “The Kornblith et al work does not endeavor to examine Alzheimer’s disease or chronic traumatic encephalopathy specifically, and findings are best compared to studies with similar endpoints (i.e., all-cause dementia).”

TBI is a risk factor for dementia, with stronger associations for injuries in older patients or that are more severe. A 2017 meta-analysis showed head injury significantly increased the risks of any dementia (RR 1.63, 95% CI 1.34–1.99) as well as Alzheimer’s disease (RR 1.51, 95% CI 1.26–1.80).

Other evidence has called an association between Alzheimer’s disease specifically and TBI into question, however: “Treating ’dementia’ as synonymous with Alzheimer’s disease in epidemiological studies may have contributed to a widespread belief that TBI is a strong environmental risk factor for Alzheimer’s disease, an association not supported in large studies with gold standard autopsy endpoints,” the editorialists wrote.

A 2019 VA Evidence Synthesis Program publication noted that TBI appeared to be associated with increased risk of dementia in veterans and called for direct comparison of dementia rates in veteran versus non-veterans and further study of the association and mechanisms.

To assess the differences in TBI-associated dementia diagnosis by sex and race, the authors identified VHA patients 55 or older who had been diagnosed with TBI between Oct. 2001 and Sept. 2015, excluding those with prevalent dementia during a 2-year baseline period prior to the date of TBI diagnosis. Veterans with prion disease or alcohol- or drug-induced dementia were also excluded.

The researchers compared this group with a random 2% sample of veterans seen by the VHA during that time, excluding individuals with prevalent dementia 2 years prior to selection.

The overall study population included 96,178 veterans with TBI and 903,464 without TBI, and was 4.3% female, 81.8% white, 11.5% Black, and 1.25% Hispanic. Median follow-up was 4.3 years.

Analysis by race showed that in each group — white, Black, and Hispanic — veterans with TBI were more likely to have low income.

“There are under-recognized and often unmeasured implicit social biases that exist in medicine with regard to race and sex that influence diagnosis and treatment decisions,” the editorialists pointed out.

“Though the observed differences remained after adjusting for a number of healthcare interactions, other unmeasured factors relating to implicit bias, stigma, barriers to care, and social determinants of health may differ by race and sex in their influence on the likelihood of having a dementia diagnosis entered into the medical record,” they added.

“The potential factors driving these racial differences in risk are perhaps just as intriguing as this novel report of the differences themselves,” they noted. These findings “should stimulate further investigation into the associations of TBI across the severity spectrum with specific neurodegenerative diseases in diverse veteran and civilian samples,” they added.

Limitations of the study include the lack of detailed information about TBI severity and mechanism. Both dementia and TBI diagnoses were recorded within the VHA system and do not necessarily include diagnoses from civilian providers or undiagnosed TBI.

Veterans who seek care in the VHA system also may differ from those who receive care in civilian healthcare settings. In addition, Asian veterans were not included in the analysis due to low sample size.

  1. Race- and sex-based differences were seen in the relationship between traumatic brain injury (TBI) and dementia diagnoses, a study of Veterans Health Administration data showed.

  2. While all race groups with TBI had increased risk of dementia diagnosis, white veterans had greatest risk.

Paul Smyth, MD, Contributing Writer, BreakingMED™

This work was supported by a Veterans Affairs Rehabilitation Research and Development Career Development Award, the National Institute on Aging, the U.S. Army Medical Research and Material Command, and the U.S. Department of Veterans Affairs.

Kornblith reported no disclosures relevant to the manuscript.

Schneider reported no disclosures. Dams-O’Connor reported relationships with the NIH, the Department of Defense Congressionally Directed Medical Research Program, Patient Centered Outcome Research Institute (PCORI), National Institute on Disability and Rehabilitation Research (NIDILRR), Brain Injury Association of America (BIAA), and various law firms.

Cat ID: 130

Topic ID: 82,130,282,494,730,130,474,192,925