Leaning beside a cooling unit, retired U.S. marine major Gamal Awad cries out while exercising at his home in Temecula, Calif. Awad has suffered from post traumatic stress disorder since he volunteered for rescue work on Sept. 11, 2001, at the Pentagon. His PTSD was aggravated by tours in Kuwait and Iraq. Researchers say veterans like Awad with post-traumatic stress disorder may have a higher risk of dementia. (Chris Carlson/Associated Press)

Veterans with post-traumatic stress disorder may have a higher risk of dementia than those without the stress disorder, a U.S. study suggests.

Life-threatening events such as war are thought to cause PTSD. Symptoms include avoiding people or things that remind someone of a trauma, nightmares, difficulty with sleep, and mood problems.

"We found veterans with PTSD had twice the chance for later being diagnosed with dementia than veterans without PTSD," said Mark Kunik, a psychiatrist at the Michael E. DeBakey VA Medical Center in Texas and senior author of the study, which appears in the September issue of the Journal of the American Geriatrics Society.

"Although we cannot at this time determine the cause for this increased risk, it is essential to determine whether the risk of dementia can be reduced by effectively treating PTSD."

The findings could have implications for veterans now returning from Afghanistan and Iraq, the researchers said.

In the study, researchers looked at the healthcare database information for 10,481 veterans at least 65 years of age who had been seen at the Texas VA Medical Center at least twice between 1997 and 1999. The researchers noted whether a vet was wounded during combat, regardless of whether they subsequently received a PTSD diagnosis, in order to have a confirmed group with injuries and combat experience.

Overall, the study's authors found 36 per cent of the veterans in the study had PTSD.

Among those with PTSD:

• 11 per cent had dementia and had not been wounded.
• 7.2 per cent had dementia and had been wounded.

In comparison, among those without PTSD:

• 4.5 per cent had dementia and had not been wounded.
• 5.9 per cent had dementia and had been wounded.

The findings held after taking into account risk factors for dementia, such as Type 2 diabetes, hypertension, heart disease and stroke.

The study's authors proposed several explanations. For example, cognitive impairment in PTSD could be an early marker of dementia, or having PTSD may make someone more likely to get dementia.

But the two conditions share some characteristics, and the findings need to be tested in a broader sample in the civilian population, the study's authors noted.

'Enormous implications'

An earlier study that analyzed a U.S. national veterans database showed similar results, with a slightly lower likelihood of dementia, at 1.77 times the rate of non-PTSD-sufferers, compared with about two times in the latest study.

The two studies reinforce and complement each other, Dr. Soo Borson of the University of Washington Medical Centre in Seattle said in a journal editorial accompanying the study.

"Confirmation of a causal link between PTSD and cognitive impairment in late life would have enormous global implications in a world facing a rising societal burden of dementia, a shrinking workforce to sustain its economies and the difficulties of containing human violence," Borson concluded.

"Soldiers and other U.S. war veterans are just one of many groups exposed to deeply traumatizing experiences with lifetime effect."

Borson also raised the question of whether the effect of traumatic brain injury is underrepresented in the research, and could be causing some of the brain dysfunction.

Promotion of dementia may also require longer exposure to more complex, chronic and severe PTSD that is less effectively treated, Borson suggested.

Civilian survivors of genocide and other politically motivated violence, victims of rape and childhood physical abuse, first responders to disasters, and people surviving severe mental illness, car collisions, violent prison environments, and sudden, unexpected deaths of loved ones are also exposed to highly traumatizing experiences.