June 7, 2010 -- Older veterans who suffer from posttraumatic stress disorder (PTSD) are almost twice as likely to develop Alzheimer's disease and other age-related dementias as veterans without PTSD, a study shows.
The study is among the first to link combat-related posttraumatic stress disorder to dementia later in life, but it is not clear if having PTSD increases the risk for late-life dementias or if recurring PTSD is an early symptom of dementia in older veterans, Deborah Barnes, PhD, of the University of California, San Francisco tells WebMD.
"We can't say from a study like this one that PTSD causes dementia," she says. "But if it does, one theory is that stress is to blame."
There is evidence that chronic stress may damage the hippocampus, which is the area of the brain that is critical for memory and learning.
PTSD and Alzheimer's
Barnes and colleagues followed more than 180,000 mostly male older veterans for seven years, including just over 53,000 with a diagnosis of PTSD. None had dementia in late 2000, but roughly 31,000 (17%) had been diagnosed with the degenerative memory and thinking disorder by late 2007.
The veterans with PTSD had about an 11% risk of developing dementia over the seven-year period, compared to about a 7% risk among veterans without the stress disorder.
After adjusting for other risk factors related to the development of Alzheimer's disease and other late-life dementias, the veterans with PTSD were 77% more likely to develop dementia as those without it.
The study was funded by the U.S. Department of Defense and the National Institute on Aging. It appears in the June issue of Archives of General Psychiatry.
"Just as with depression, it is common for people to cycle in and out of PTSD for many years or even decades," Barnes says. "One message is that when we see PTSD symptoms in older veterans that could be a sign of other problems."
PTSD Common in Old and Young Vets
PTSD is common among combat veterans, even decades after the fighting ends. In one study of older World War II and Korean veterans, as many as 12% were still reporting symptoms 45 years after their service ended.
Studies of Vietnam veterans suggest that 10% to 15% still suffered from PTSD a decade and a half or longer after returning from combat.
In a recent study of veterans returning from Iraq and Afghanistan, 17% suffered from posttraumatic stress disorder.
Psychiatrist Gary Kennedy, MD, who directs the division of geriatric psychiatry at New York's Montefiore Medical Center, says treating PTSD in wounded veterans returning from Iraq and Afghanistan will pose a particular challenge because so many have traumatic brain injuries due to exposure to roadside improvised explosive devices (IEDs).
"We have gotten very good at saving lives on the battlefield, but we are not so good at dealing with the brain injuries that occur as a result of IED exposure," he tells WebMD. "It is a good bet that the risk for dementia is much higher when PTSD is complicated by brain injury."