SAN FRANCISCO — The risk of dementia is increased even in veterans who suffer mild traumatic brain injury (TBI) without loss of consciousness.

That’s according to a study of more than 350,000 U.S. veterans published in JAMA Neurology.1

Background information in the article noted that TBI is common among both veterans and civilians and can be caused by shockwaves from blasts, as well as blunt force. In many cases, loss of consciousness does not occur.

A study team led by researchers from the Veterans Health Care System and the University of California, both in San Francisco, pointed out that moderate and severe TBIs have previously been associated in some studies with increased dementia risk but no clear association had been demonstrated between dementia and mild TBI, especially without loss of consciousness.

Their observational study focused on 178,779 patients diagnosed with TBI at the VHA from 2001 to 2014. An equal number of veterans without TBI was used as a control group for comparison. Veterans had a mean age of nearly 49.5 years at baseline, with 9.3% women and 72.5% non-Hispanic whites.

They found that, even after accounting for medical and psychiatric coexisting conditions, the risk for dementia was increased for mild TBI without a loss of consciousness (LOC), mild TBI with LOC, mild TBI when it was unknown if there was LOC and for moderate to severe TBI.

The researchers reported that differences between veterans with and without TBI were small, with 2.6% of veterans without TBI developing dementia, compared with 6.1% of those with TBI.

After adjustment for demographics and medical and psychiatric comobidities, adjusted hazard ratios for dementia were calculated as 2.36 (95% CI, 2.10-2.66) for mild TBI without LOC, 2.51 (95% CI, 2.29-2.76) for mild TBI with LOC, 3.19 (95% CI, 3.05-3.33) for mild TBI with LOC status unknown and 3.77 (95% CI, 3.63-3.91) for moderate to severe TBI.

“In this cohort study of more than 350 000 veterans, even mild TBI without LOC was associated with more than a 2-fold increase in the risk of dementia diagnosis,” the study authors concluded. “Studies of strategies to determine mechanisms, prevention, and treatment of TBI-related dementia in veterans are urgently needed.”

1Barnes DE, Byers AL, Gardner RC, Seal KH, Boscardin WJ, Yaffe K. Association of Mild Traumatic Brain Injury With and Without Loss of Consciousness With Dementia in US Military Veterans. JAMA Neurol. 2018 May 7. doi: 10.1001/jamaneurol.2018.0815. [Epub ahead of print] PubMed PMID: 29801145.