A study of over 350,000 US soldiers has linked traumatic brain injury with an increased risk of dementia.

Researchers used data from the Veterans Health Administration to compare over 178,000 veterans with a traumatic brain injury with an equal number of their comrades who did not have such an injury.

Traumatic brain injury (TBI), even mild TBI without a loss of consciousness, was associated with increased risk for dementia.

TBI is common among veterans and civilians. In the military, TBI can be caused by shock waves from blasts, as well as blunt force, and it may not result in a loss of consciousness.

Moderate and severe TBIs have previously been associated in some studies with increased dementia risk but an association between dementia and mild TBI, especially without an accompanying loss of consciousness, has been unclear.

The report found 6.1 per cent of vets with TBI had dementia, while just 2.6 per cent of vets without TBI had dementia.

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 study is accessible here.