"The medical community has never researched the simultaneous impact of post-traumatic stress disorder (PTSD), traumatic brain injury (TBI), and genetic risk factors in a large cohort until now.
In a study of Veterans led by Dr. Mark Logue, a statistician in the National Center for PTSD at the VA Boston Healthcare System, researchers concluded that PTSD, TBI, and the 4 variant of the APOE gene showed strong associations with Alzheimer"s Disease and related dementias (ADRD).
The researchers first found a greater percentage of ADRD in Veterans with PTSD and in those with TBI, relative to those without, as well as higher rates of ADRD in Veterans who had inherited the 4 variant. Logue and his team then looked for interactions between the 4 variant, PTSD, and TBI using a mathematical model.
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The study found an increase in risk due to PTSD and TBI in Veterans of European ancestry who inherited the 4 variant. In Veterans of African ancestry, the impact of PTSD didn"t vary as a function of 4, but the TBI effect and interaction with 4 was even stronger. Other studies have suggested that 4 may magnify the effects of a head injury and/or combat-related stress.
"These additive interactions indicate that ADRD prevalence associated with PTSD and TBI increased with the number of inherited APOE 4 alleles," Logue and his colleagues wrote. "PTSD and TBI history will be an important part of interpreting the results of ADRD genetic testing and doing accurate ADRD risk assessment.""