Post-traumatic stress disorder as a risk factor for dementia: systematic review and meta-analysis.

Background: Post-traumatic stress disorder (PTSD) has been identified as a potential risk factor for developing dementia. There are currently, however, no meta-analyses quantifying this risk.

Aims: To systematically review and quantify the risk of future dementia associated with PTSD across populations. PROSPERO registration number CRD42019130392.

Method: We searched nine electronic databases up to 25 October 2019 for longitudinal studies assessing PTSD and risk of dementia. We used random- and fixed-effects meta-analyses to pool estimates across studies.

Results: PTSD was associated with a significant risk for all-cause dementia: pooled hazard ratio HR = 1.61 (95% CI 1.43-1.81, I2= 85.8%, P < 0.001; n = 1 693 678; 8 studies). Pooled HR was 1.61 (95% CI 1.46-1.78; I2= 80.9%, P < 0.001; n = 905 896; 5 studies) in veterans, and 2.11 (95% CI 1.03-4.33, I2= 91.2%, P < 0.001; n = 787 782; 3 studies) in the general population. The association between PTSD and dementia remained significant after excluding studies with high risk of bias (HR = 1.55, 95% CI 1.39-1.73, I2= 83.9%, P < 0.001; n = 1 684 928; 7 studies). Most studies included were retrospective and there was evidence of high heterogeneity.

Conclusions: This is the first meta-analysis quantifying the association of PTSD and risk of dementia showing that PTSD is a strong and potentially modifiable risk factor for all-cause dementia. Future studies investigating potential causal mechanisms, and the protective value of treating PTSD are needed.