CHICAGO (Reuters) - Older veterans who have had post-traumatic stress disorder have nearly double the risk of dementia than other veterans, U.S. researchers said on Monday.
The findings, presented at an Alzheimer's Association meeting in Vienna, are the first to link PTSD -- a debilitating anxiety disorder that can be caused by wartime trauma -- with dementia.
"The million-dollar question is why," Dr. Ronald Petersen of the Alzheimer's Association and an Alzheimer's researcher at the Mayo Clinic in Rochester, Minnesota, said in a telephone interview.
Some studies have found PTSD was linked with diminished brain volume in the hippocampus, a part of the brain involved in memory and stress response.
Alzheimer's is the most common form of dementia, which is marked by a loss of memory and other cognitive, or thinking, abilities, including the ability to speak, identify objects or think abstractly.
Some older veterans with PTSD have shown signs of cognitive declines. Dr. Kristine Yaffe of the University of California, San Francisco, analyzed data on 53,155 veterans diagnosed with PTSD and 127,938 veterans without PTSD, using the Department of Veterans Affairs National Patient Care Database.
Veterans in the study had an average age of 69.
More than 10 percent of veterans with PTSD developed new cases of dementia, compared with 6.6 percent of those who did not have PTSD.
Even after adjusting for other dementia risk factors, such as traumatic brain injury or depression, veterans with PTSD still had double the risk compared with other veterans in the study.
"Further research is needed to fully understand what links these two important disorders," Yaffe said in a statement.
"With that knowledge we may be able to find ways to reduce the increased risk of dementia associated with PTSD," she said.
Editing by Maggie Fox