First author Dr. Salah Qureshi at the Michael E. DeBakey Veterans Administration Medical Center in Houston notes -- despite the increased risk -- most veterans with PTSD did not develop dementia during the study period.
The study, published in the Journal of the American Geriatrics Society, finds among veterans who had PTSD, 11.1 percent who had not been injured in combat, and 7.2 percent who had been injured, had dementia -- vs. 4.5 percent and 5.9 percent, respectively, among those without PTSD.
The results remain significant even after other risk factors for dementia -- such as high blood pressure -- are taken into account.
"It will be important to determine which veterans with PTSD are at greatest risk and to determine whether PTSD induced by situations other than war injury is also associated with greater risk," Qureshi says in a statement.
Qureshi and colleagues gathered information until 2008 for 10,481 veterans at least 65 years of age who had been seen at the VA Medical Centre at least twice between 1997 and 1999.