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

Dementia is a major cause of disability for the world's older population, representing the biggest global challenge of the 21st century.¹ Around 50 million people live with dementia worldwide, with prevalence rates expected to triple by 2050.² Given the lack of disease-modifying treatments, the identification and prevention of modifiable risk factors for dementia is an important public health priority.¹ Post-traumatic stress disorder (PTSD) has recently been identified as a potential risk factor for developing dementia.^3–5 However, despite the increased importance of this association across a range of populations, evidence of the magnitude of this relationship and potential mechanisms remain unknown. PTSD is a stress-related disorder developing after exposure to a traumatic stressor such as (threatened) death, serious injury or abuse,⁶ with an increased conditional risk of a PTSD diagnosis around 4%.⁷ Symptoms of PTSD, such as re-experiencing the traumatic event, avoidance and hypervigilance, often remain untreated for years, resulting in a chronic condition severe enough to affect daily functioning.^8,9

PTSD is understood to arise as a result of strong negative appraisals of the trauma and disturbances in autobiographical memory.¹⁰ Recent studies show that PTSD is associated with poor cognitive outcomes in several neurocognitive domains, such as processing speed, attention and working memory.¹¹ Neural structural changes contributing to poor cognitive function have also been observed, although evidence suggests that the association between PTSD and impaired cognition is bidirectional.¹² Given the complexity of multiple risk factors contributing to dementia, estimating the risk associated with PTSD is important for informing future preventive strategies.¹

Although a systematic review examining the relationship between PTSD and dementia is now available,⁵ there are currently no meta-analyses. Given the lack of data on the magnitude of the relationship between PTSD and dementia, and a number of new studies being published, our primary objective in this study was to conduct the first meta-analysis of the relationship between PTSD and all-cause dementia in the literature. A secondary objective was to review the quality of the evidence.

Method

We followed current guidelines for systematic reviews and meta-analyses¹³ and registered the review with PROSPERO¹⁴ (CRD42019130392).

Search strategy

We searched nine databases (MEDLINE, Embase, PsycINFO, CINAHL Plus, ProQuest Dissertations & Theses Global, EThOS, OpenGrey,...