Blood-Based Biomarkers for Alzheimer's Disease in Older Adults with Posttraumatic Stress Disorder

Background: Posttraumatic stress disorder (PTSD) is associated with cognitive decline and risk for dementia, but the neuropathology involved is unclear. Objective: The aim of this study was to determine whether PTSD is associated with increased levels of Alzheimer's disease (AD) blood-based biomarkers. Methods: Individuals aged 50 years and older with PTSD were compared to trauma-exposed healthy controls (TEHCs) at baseline on serum measures of amyloid-beta (A beta) 42 and 40 levels, the A beta(42)/A beta(40) ratio, and total tau. Serum was analyzed using ultrasensitive Simoa Human Neurology 3-Plex A assay (N3PA). Linear regressions modeling each AD biomarker as a function of group were used to investigate between-group differences, controlling for age, sex, and educational attainment (years). Results: TEHC participants (N= 26) were 53.8% male with mean age 66.8 +/- 10.7, whereas PTSD participants (N= 44) were 47.7% male and aged 62.5 +/- 9.1 years. No between-group differences were noted on demographic characteristics or cognitive performance measured with the NIH Toolbox Cognition Battery. There were no significant between-group differences in serum A beta(40) (TEHC 105.8 +/- 51.6 versus PTSD 93.2 +/- 56.1, p = 0.46), A beta(42) (TEHC 8.1 +/- 4.6 versus PTSD 7.8 +/- 4.6, p = 0.63), A beta(42)/A beta(40) (TEHC 0.08 +/- 0.03 versus PTSD 0.09 +/- 0.03, p = 0.27), or total tau (TEHC 0.5 +/- 0.3 versus PTSD 0.5 +/- 0.4, p = 0.77). Likewise, there were no significant interaction effects of amyloid or tau serum concentrations and PTSD group status on cognitive functioning. Conclusion: Findings from cognitive assessments and serum analyses do not support PTSD-induced neurodegeneration of the Alzheimer's type as a pathway linking PTSD to increased incidence of dementia in older adults.