(Reuters Health) - - Female military veterans with traumatic brain injury, post-traumatic stress disorder or depression are more likely to develop dementia later in life than peers without those conditions, a U.S. study suggests.

Each of those conditions was associated with an increased risk for dementia, and if a female vet was diagnosed with more than one, that risk went up, researchers report in Neurology.

Earlier studies have made the same connections for male veterans, said lead author Dr. Kristine Yaffe, who is chief of neuropsychiatry at the San Francisco Veterans Affairs Medical Center.

“We really need to study older women veterans more to try to understand their health as they age,” said Yaffe. “I think this area is wide open and has, frankly, been ignored. Our study suggests these people should probably be followed more closely so changes in cognition can be detected earlier, giving us a chance to try to improve outcomes for them.”

Findings in female vets might also apply to other women, Yaffe said. “While these military risk factors are more common in veterans, they are not unique to the military,” she said.

Yaffe and colleagues analyzed health records for all women ages 55 to 110 in the Veterans Health Administration database who were evaluated from October 2004 through September 2015.

At the time they were examined, none of the 109,140 women in the study had dementia. But 20,140 had a diagnosis of depression only, 1,363 had PTSD only, 488 had traumatic brain injury (TBI) only, and 5,044 had more than one of these military-related risk factors.

During the next four years, 4,125 women, or 4 percent of the entire group, were diagnosed with dementia. Rates of dementia were 3.4 percent in women without brain injury or one of the mental health diagnoses, 5.2 percent in women with depression, 5.7 percent with TBI and 3.9 percent with PTSD.

Overall, the women with any single military-related risk factor had a 50 to 80 percent increased risk of dementia. Women with multiple risk factors had nearly double the risk of dementia compared to those who had none.

Yaffe notes that one limitation of the study is that the information on the women came from codes entered by the doctors who made those diagnoses. It’s possible, she said, that some women with less severe symptoms might have been missed.

It’s also important to note that the study found “associations” between these diagnoses and dementia, rather than proof that they cause the condition, said Dr. Douglas Smith, director of the Center for Brain Injury and Repair at the University of Pennsylvania in Philadelphia, who wasn’t involved in the study.

Of the three conditions studied, TBI has the best evidence to suggest it might cause changes that could lead to dementia, he said.

Smith suspects that some of the female vets with PTSD may also have had undiagnosed TBIs. “There’s an overlap between a history of TBI and a history of PTSD,” Smith said. “Often the two come together and in some cases it’s hard to differentiate between the two.”

Beyond that, military people often don’t realize they’ve had a mild TBI, or concussion, when it happens, Smith said. “In this group, PTSD might be more of an indicator that a person has had a TBI,” he added. “The researchers have taken on a very messy topic, with severe TBIs, concussions, PTSD and depression all blended together and tried to make sense of it. I think they did a good job with the data they had.”

SOURCE: bit.ly/2GpRYiD and bit.ly/2LeY4AO Neurology, online December 12, 2018.