FRIDAY, Jan. 6, 2023 (HealthDay News) -- Posttraumatic stress disorder (PTSD) and traumatic brain injury (TBI) interact with apolipoprotein E (APOE) ε4 to confer increased prevalence of Alzheimer disease and related dementias (ADRD) in veterans, according to a study published online Dec. 22 in Alzheimer's & Dementia.
Mark W. Logue, Ph.D., from the VA Boston Healthcare System, and colleagues examined the impact of APOE ε4, PTSD, and TBI on the prevalence of ADRD in veteran cohorts of European ancestry (EA; 11,112 ADRD cases and 170,361 controls) and African ancestry (AA; 1,443 ADRD cases and 16,191 controls) from the Million Veteran Program.
The researchers identified strong main-effect associations for PTSD, TBI, and APOE ε4 with ADRD. In a relative excess risk due to interaction analysis, significant additive APOE ε4 interactions were seen with PTSD and TBI and with TBI in the EA and AA cohorts, respectively. These additive interactions indicated that the prevalence of ADRD associated with PTSD and TBI was increased with an increasing number of inherited APOE ε4 alleles.
"Tests can only give an estimate of your likelihood of developing Alzheimer's that may be higher or lower than average. Our study shows that these estimates will be more accurate if they incorporate more than just age and genetics," Logue said in a statement. "In Veterans, a history of head injuries and PTSD can also make a large difference in dementia risk, so using that information will allow for more accurate measurement of the chances of developing dementia."