London, Sep 16 : People who have experienced post-traumatic stress disorder (PTSD) are up to twice as likely to develop dementia later in life, warn researchers.
For the study, published in the British Journal of Psychiatry, the researchers analysed findings from 13 studies conducted on four continents on PTSD and dementia risk.
"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," said study author Vasiliki Orgeta from the University College London (UCL) in the UK.
The research team included 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 data from eight of the studies, the researchers found that people with PTSD faced a 61 per cent higher risk of dementia.
Analysing data from two studies that used different methods, they found that PTSD was associated with double the odds of developing dementia.
The researchers say the risk could be higher than the studies suggest, as PTSD also increases the likelihood of developing other known dementia risk factors, such as depression, social isolation, or elevated alcohol intake.
Most of the studies adjusted for some of these factors, so the overall findings might underestimate the true cost of PTSD.
It remains unclear how PTSD raises dementia risk, but the researchers say it may be related to hypervigilance and recurrent re-experiencing of trauma, contributing to threat and stress-related activity in the brain, while withdrawal from social life may reduce cognitive reserve and resilience.
"Our findings add to a growing body of evidence that dementia can sometimes be prevented by addressing risk factors throughout an individual's life course," said study author Mia Maria Gunak from UCL.
"Here we have identified an additional group of people who face an elevated risk of dementia, who may benefit from further mental health support," Maria added.