TBI, PTSD Not Linked With Biomarker-Defined Alzheimer Disease
Traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD) were associated with an increased prevalence of mild cognitive impairment but not Alzheimer disease biomarkers in a study of Vietnam veterans, according to a new study published in Alzheimer’s & Dementia.
“Our results suggest that TBI or PTSD or TBI/PTSD together do not contribute to an increase or acceleration in Alzheimer’s disease biomarkers,” wrote study lead author Michael W. Weiner, MD, Department of Veterans Affairs Medical Center, San Francisco, California, and coauthors.
Prompted by reported associations between TBI and PTSD, and clinically diagnosed Alzheimer disease in epidemiological studies, the researchers evaluated 289 veterans with TBI and/or PTSD and controls to assess for links with biomarker-defined Alzheimer disease. Participants underwent clinical evaluation as well as cerebrospinal fluid collection, magnetic resonance imaging (MRI), amyloid beta and tau positron emission tomography, and apolipoprotein E testing.
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Compared with controls, the prevalence of mild cognitive impairment was higher in participants with TBI, PTSD, or both, and Mini-Mental State Examination scores were lower, according to the study. Nevertheless, researchers identified no significant differences in other cognitive scores, MRI volumes, amyloid beta or tau accumulation, or most longitudinal measures over as many as 5.2 years of follow-up.
“This information raises questions about alternative mechanisms underlying cognitive symptoms and Alzheimer’s disease diagnosis in these patients,” researchers wrote.
The discrepancy in the findings with the well-documented association between TBI/PTSD and increased frequency of dementia could be explained by differing definitions of Alzheimer disease, researchers suspect. Their study used a biological definition of Alzheimer disease based on underlying neuropathology, whereas most epidemiological studies use a broader clinical and behavioral definition of Alzheimer disease dementia.
“The clinical diagnosis of Alzheimer’s disease dementia is based on clinical evaluations of patients drawn from both community samples and specialty clinics over time with evolving diagnostic criteria related to cognitive symptoms and functional decline that interferes with daily activities,” they wrote, “and may include a range of progressive neurodegenerative diseases.”
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