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Studies find intriguing link between PTSD, dementia

December 9, 2010

Army Veteran Hubert McCarty meets with Mark Kunik, M.D., M.P.H., a psychiatrist at the Michael E. DeBakey VA Medical Center.  

Army Veteran Hubert McCarty meets with Mark Kunik, M.D., M.P.H., a psychiatrist at the Michael E. DeBakey VA Medical Center. “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,” said Kunik.

HOUSTON - Study results reported this month in the Journal of the American Geriatrics Society suggest that Veterans with posttraumatic stress disorder (PTSD) have a higher risk for dementia than their peers without PTSD. The authors emphasize that while PTSD was associated with higher risk, the great majority of Veterans with PTSD in the study did not develop dementia.

"We found Veterans with PTSD had twice the chance for later being diagnosed with dementia than Veterans without PTSD," says Mark Kunik, MD, MPH, a psychiatrist at the Michael E. DeBakey VA Medical Center in Houston and senior author of the article. "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. This could have enormous implications for Veterans now returning from Iraq and Afghanistan."

The study included 10,481 Veterans at least 65 years of age, almost all men. One group had a PTSD diagnosis and had received a Purple Heart for having been wounded in action. A second group had a Purple Heart but no PTSD, and a third group PTSD but no Purple Heart. This way, the researchers could tease out the effects of PTSD versus combat trauma that did not lead to PTSD. A fourth set of Veterans with neither PTSD nor a Purple Heart served as a comparison group.
Of the four groups, those with PTSD and no Purple Heart had the highest prevalence of dementia—about 11 percent. Next was the PTSD group with a Purple Heart, at 7 percent. The other two groups were at 6 percent, for those with a Purple Heart and no PTSD; and about 5 percent, for those with neither. The differences remained even after the researchers adjusted for factors such as traumatic brain injury, substance abuse and heart disease.

Overall, the rates in the study may be lower than those seen in the American population at large. A major National Institutes of Health study published in 2007 estimated the prevalence of dementia among Americans age 71 and older to be 14 percent. This was a somewhat older group, though, and dementia risk does increase with age.

Lead author Salah Qureshi, MD, a staff psychiatrist at the Houston VA, says a future research goal will be pinpointing factors that help explain why some Veterans with PTSD develop dementia while others do not. "Despite the increased risk for those with PTSD, it is noteworthy that most Veterans with PTSD did not develop dementia during the period we studied," he says. "It will be important to determine which Veterans with PTSD are at greatest risk and … whether PTSD induced by situations other than war injury is also associated with greater risk."

The authors note there could be several explanations for their findings. It could be that both PTSD and dementia share certain underlying risk factors, or that PTSD itself is a risk factor for dementia.

A separate study by a VA group in San Francisco, published in June 2010 in the Archives of General Psychiatry, also found a roughly doubled risk for dementia among Veterans with PTSD. That study looked at much larger sample—more than 181,000 Veterans. The incidence rates were about the same as those seen in the Houston study. Lead author on the San Francisco study, psychiatrist Kristine Yaffe, MD, offered theories similar to Kunik's on how PTSD and dementia may be linked. Among other possible explanations, she said, PTSD may alter the production of stress hormones in a way that eventually damages the hippocampus, a brain area crucial for memory; or certain pre-existing genetic factors may boost the risk of both conditions.

This article originally appeared in the September 2010 issue of VA Research Currents.**