Dose-related trajectories
Results showed that having more PTSD symptoms was associated with dose-related poorer cognitive trajectories.
After adjustment for demographic characteristics, women with the highest symptom level (six to seven symptoms) had a significantly worse rate of change in both composite domains of learning and working memory (beta = −0.08 SD/y; 95% confidence interval [CI], −0.11 to −0.04 SD/y; P < .001) and of psychomotor speed and attention (beta = −0.05 SD/y; 95% CI, −0.09 to −0.01 SD/y; P = .02) compared with women with no PTSD symptoms.
Women with four to five PTSD symptoms showed a worse rate of change in learning and working memory compared with those who had no symptoms, but not in psychomotor speed and attention. Women with one to three PTSD symptoms had cognitive scores similar to those of women without PTSD symptoms.
Notably, the associations of PTSD with cognitive change remained evident after additional adjustment for behavioral factors and health conditions – and were only “partially attenuated but still evident” after further adjustment for practice effects and comorbid depression, the investigators wrote.
“We thought PTSD might be associated with worse cognitive decline through health behaviors like smoking and alcohol drinking and higher risk of other health conditions like hypertension and depression,” Ms. Liu said.
However, those factors did not account for the current study’s findings, she noted.
“We could not determine why women with PTSD had faster cognitive decline than those without PTSD,” she said.
Ms. Liu suggested that PTSD “may have effects on the brain, such as altering brain structures and affecting brain immune function.” However, more research is needed “to investigate these mechanisms that might underlie the association we found between PTSD and cognitive decline,” she said.
Neurotoxic effect
In a comment, Howard Fillit, MD, cofounder and chief science officer of the Alzheimer’s Drug Discovery Foundation, said, “It is well known that stress is neurotoxic, and PTSD is a particularly serious form of stress.”
Dr. Howard Fillit
Dr. Fillit, clinical professor of geriatric medicine and palliative care, medicine, and neuroscience at Mount Sinai Hospital, New York, was not involved with the study.
“We tend to think of PTSD in postacute settings, such as soldiers returning from war,” he said. “This study contributes to our understanding of the long-term effects of PTSD on cognitive decline, measured objectively over time”
Dr. Fillit noted that an important implication is that, by increasing the risk for cognitive decline, PTSD also increases risk for Alzheimer’s disease. This leads to the “main take-home, which is that PTSD is a risk factor not only for cognitive decline but also for Alzheimer’s and related dementias,” he said.
However, this opens a potential therapeutic approach, Dr. Fillit added.
Because cortisol and other stress hormones drive the stress response, finding ways to block the neurotoxic effects of these hormones “might be a target to prevent cognitive decline and decrease Alzheimer’s disease risk,” he said.
The study was supported by grants from the National Institute of Mental Health and the National Institutes of Health. Ms. Liu and Dr. Fillit report no relevant financial relationships.
A version of this article first appeared on Medscape.com.