Veterans who suffered a traumatic brain injury may be at greater risk of developing dementia later in life, says a new U.S. study that looks at the possible link between the neurological disorder and the signature wound of the Afghanistan conflict.

The research, published Wednesday in the online journal Neurology, also found that veterans with a history of traumatic brain injury, or TBI, developed dementia about two years earlier than those without a brain injury but who had dementia.

The findings add to a growing, but disputed body of research involving professional athletes and military members that suggest brain trauma can be linked to neurological disorders that appear to set in years after the event.

"This study convincingly shows that mild trauma has a role in increasing the risk of dementia," said Rodolfo Savica, a member of the American Academy of Neurology who wrote an editorial accompanying the study.

"(It) sheds light on the more complex relationship between medical and psychiatric diseases with TBI in the development of the future risk of dementias."

The research by doctors at the University of California in San Francisco involved 189,000 American veterans who were 68 years old on average at the start of the study.

None had dementia at the beginning of the project, which spanned nine years and was supported by the U.S. Department of Defense.

Of the 1,229 veterans who were diagnosed with TBI, 196 — or 16 per cent — developed dementia compared to 10 per cent with TBI who didn't.

Deborah Barnes of the University of California and the report's author, found veterans who had TBI but did not develop dementia died 2.3 years earlier than those without a brain injury.

The authors say that after adjusting for other factors that could affect the risk of dementia, such as diabetes and alcohol abuse, they found that "veterans with TBI were 60 per cent more likely to develop dementia than those without TBI."

Savica stressed that those other factors could play a significant role in the development of dementia in veterans with TBI and that a definitive, causal link can't be made between TBI and the neurological disorder.

A doctor with the Canadian Forces said he didn't know of any similar type of study involving soldiers in this country who have sustained brain injuries, which the military started screening for in 2009 during operations in Afghanistan.

Dr. Bryan Garber, a senior epidemiologist with the Canadian Forces' directorate of mental health, said it would be ideal to conduct a study that follows people soon after a traumatic brain injury.

"It potentially points to a possible concern with regards to a realistic long-term outcome which talks to the issue of trying to reduce the risk of harm," he said.

"But the down side of these reports is that they create fear in the population to the extent that someone might say, 'I'll never let my kid go on to a soccer pitch.'"

He said the Forces screened 16,153 personnel who deployed in Afghanistan from 2009 to 2012. Out of that, mild traumatic brain injury was reported in 843 respondents, or 5.2 per cent.

No one from Veterans Affairs was available for comment.

Savica said they discovered that the risk of dementia was higher in veterans with TBI who also had depression, post-traumatic stress disorder or cardiovascular disease than in those with either TBI or these other conditions alone.

News from © The Canadian Press, 2014