A new study found that PTSD increases dementia risk by 61 percent — findings that are especially pertinent for soldiers and veterans, and new and growing population with PTSD: survivors of COVID-19.
People living with post-traumatic stress disorder (PTSD) are more than twice as likely to develop dementia later in life than those without PTSD, according to a new study by researchers at University College London. The research’s implications are far-reaching as experts warn that survivors of COVID-19 are at high risk of PTSD and should be screened for the disorder.
The review, published in the British Journal of Psychiatry, is the first meta-analysis of global evidence on PTSD and dementia risk. UCL researchers analyzed findings from 13 studies conducted on four continents, including data from a total of 1,693,678 people, investigating whether a PTSD diagnosis was associated with increased risk of dementia up to 17 years later.
By pooling this vast amount of data, they found PTSD increases a person’s risk of developing dementia by 61 percent.
“Our study provides important new evidence of how traumatic experiences can impact brain health, and how the long-term effects of trauma may impact the brain in many ways increasing vulnerability to cognitive decline and dementia,” senior author Dr. Vasiliki Orgeta at UCL Psychiatry said in a news statement.
Orgeta and colleagues’ findings are in line with previous research, which shows that veterans diagnosed with PTSD were at a nearly two-fold-higher risk of developing dementia than with those without PTSD, and that held true among both men and women.
Indeed, Orgeta’s study shows that dementia risk among people who have had PTSD in the general population were more likely to develop dementia compared to veterans with PTSD; people in the general population with a PTSD diagnosis were more than twice as likely to develop dementia.
Orgeta and colleagues said that in the countries the studies were conducted, veterans are typically more likely to receive treatment for PTSD, so the findings suggest that PTSD treatment may help reduce subsequent dementia risk. But there are other populations for whom the disorder is prevalent, and one new and growing population is patients who have recovered from COVID-19.
“PTSD, which appears to be common among people who have been hospitalized with COVID-19, remains an under-diagnosed, under-treated, and under researched mental health condition, yet it can have serious long-term consequences,” he said. “A lot of people with PTSD don’t access treatment, sometimes due to a lack of mental health care capacity but also because of stigma which often keeps people away from seeking help. We now have more evidence of how traumatic experiences and accessing treatment could have a long-lasting impact for individuals and influence future risk of developing dementia.”
Because PTSD increases the likelihood of a person developing other known risk factors for dementia, including depression, social isolation or alcoholism, most of the studies in Orgeta’s review adjusted for some of these factors, he said, so the overall findings might underestimate the true cost of PTSD. In other words, increased risk could be even higher.
Why does PTSD increase dementia risk?
The causal link between PTSD and dementia remains unknown, but the researchers say it may be related to people’s hyper-vigilance and continued re-experiencing of trauma, contributing to threat and stress-related activity in the brain. Recent studies have found that repetitive negative thinking — ruminating on past bad experiences — is associated with higher levels of harmful tau and beta-amyloid proteins in the brain — key biomarkers of Alzheimer’s.
Further, trauma may prompt a withdrawal from social life. Loneliness and isolation are known to reduce cognitive reserve and resilience. In fact, loneliness has been found to increase dementia risk by up to 40 percent.
According to Daniela Kaufer from the Helen Wills Neuroscience Institute and the University of California, Berkeley, one theory for this link is that the stress caused by PTSD, while it may not cause Alzheimer’s, makes brain cells more vulnerable, and if the genetic factors that lead to Alzheimer’s are already present, a person would be more susceptible to developing the disease.
“From a young brain to a mature brain, there are different stages of vulnerability and the impact of stress. Research has shown that some stress can be beneficial and change the structure and function of the hippocampus. Other research has shown how stress can be detrimental to memory function, causing anxiety and depression,” Kaufer told Being Patient in a BrainTalk.
“An earlier false belief was that stress increases the number of cells that are dying in your brain. However, stress itself does not kill brain cells. Those cells become more vulnerable to secondary hits. So when something else besides stress comes along, those cells are much more vulnerable, and are more likely to die. When a toxic protein aggregates, like you would see in a neurocognitive disorder like Alzheimer’s, and that comes on top of a stressed brain, the cells are more susceptible. It can exacerbate the damage you can get from a neurocognitive disorder. It makes us more susceptible to damage from other conditions. So it doesn’t make you more likely to develop Alzheimer’s, but if you have Alzheimer’s and the brain is very stressed, then those cells are more likely to die.”
Next steps
“As our study has shown, PTSD impacts our brain health by increasing vulnerability to dementia,” Orgeta said. “An important question is how, and whether we could learn from these findings to develop preventative treatments for those with elevated risk.”
“Here we have identified an additional group of people who face an elevated risk of dementia, who may benefit from further mental health support.”
