Older veterans with post-traumatic stress disorder are nearly twice as likely to develop dementia as their peers without PTSD, according to research released today.
Dr. Kristine Yaffe of the University of California, San Francisco, and the San Francisco Veterans Affairs Medical Center and her colleagues followed more than 180,000 veterans aged 55 and older for seven years. All were free from dementia at the study's outset, while about 30 percent had PTSD.
Nearly 11 percent of the vets with PTSD developed dementia during follow-up, compared to only about 7 percent of those who didn't have PTSD.
Once the researchers took into account factors such as other physical or mental health problems, they found that vets with PTSD were still nearly twice as likely to develop dementia.
"PTSD is a pretty common diagnosis, sadly, that does seem to occur in roughly maybe 10 percent of combat-exposed veterans," Yaffe noted in an interview with Reuters Health. "This is not a short-lived thing necessarily ... probably in a third or possibly more it's a chronic disorder."
While it's unknown how PTSD might up dementia risk, the researcher noted, it's possible that years of stress can cause lasting changes in the brain. "The implications in terms of taking care of patients with PTSD, particularly as they age, are pretty big," she added. "It's going to be an area that's important for us to understand better."
Yaffe and her colleagues report their findings in the latest issue of Archives of General Psychiatry.
A related study in the journal suggests that National Guard soldiers suffer more from PTSD and depression than their active-duty peers after returning from combat duty in Iraq.
Twelve months after returning home, Dr. Jeffrey L. Thomas of the Walter Reed Army Institute of Research in Silver Spring, Maryland and his colleagues found, the National Guard soldiers' symptoms had actually gotten worse, while they remained stable for the active-duty soldiers.
Levels of combat exposure were the same for National Guard and regular Army troops in the current study, despite the common misconception that Guard soldiers don't face as much battle time, Thomas noted in an interview. "These guys were trigger pullers, they were kicking in doors, they were doing all the same things" as active duty troops, he said.
While PTSD and depression are known to plague combat veterans who served in Iraq and Afghanistan, Thomas and his colleagues note, studies looking at how common these problems are have used a variety of different criteria for assessing mental health problems. They also haven't looked at how impaired vets may be by their symptoms, or whether affected vets are also prone to misuse alcohol or behave aggressively.
To investigate, Thomas and his team surveyed 18,305 Army soldiers 3 and 12 months after deployment to Iraq or Afghanistan. In the current analysis, they looked at 13,226 men and women serving in Iraq, including four active duty infantry brigade combat teams and three National Guard infantry brigade combat teams.
The researchers used seven different case definitions of PTSD, and three different case definitions of depression. Study participants also reported whether they had got angry with someone and slammed a door or punched a wall, etc; threatened someone with violence; or had a physical fight with someone. People who reported doing this at least once were considered to have behaved aggressively.
Overall, based on the definition used, 21 percent to 31 percent of the vets had PTSD, while 12 percent to 16 percent had depression.
Again, depending on the criteria used, Thomas and his colleagues found that 8.5 percent to 14 percent of the vets had PTSD or depression with serious functional impairment, while 23.2 percent to 31.1 percent had PTSD or depression with some impairment. Half of the individuals who had depression or PTSD also abused alcohol or behaved aggressively.
While PTSD symptoms got worse between the 3- and 12-month surveys for both active duty and National Guard troops, they increased much more sharply in the Guard soldiers. The prevalence of depression remained stable for the active duty soldiers, but increased for the Guard soldiers.
When the researchers used the strictest definitions of depression and PTSD, they found 4 percent of the National Guard troops reported depression or PTSD plus alcohol abuse or aggressive behavior; this percentage rose to 8 percent by 12 months.
Many factors are likely involved in why Guard soldiers might fare worse, Thomas said in an interview; for example, regular Army vets have uninterrupted access to health care, but National Guard soldiers' coverage ends six months after they return from duty. National Guard vets must transition back to civilian life with relatively little support from the military, or from Guard peers also returning from combat.