The prevalence of a Traumatic Brain Injury (TBI) seems to correlate with the likelihood of receiving a diagnosis of Alzheimer’s Disease (AD) later in life. Contemporary literature shows that a TBI puts an individual at greater risk for developing dementia; however, there seems to be a gap in the literature identifying the cognitive differences in AD between those with and without a history of TBI. The present research seeks to explore the impact of TBIs on the cognitive abilities of those with AD.

A total of 156 patients (79 female, M age = 77.82, M education = 14.21) diagnosed with AD participated in outpatient neuropsychological assessment. Participants completed measures of frontal-executive functioning, visuospatial ability, processing speed, simple attention, language, and both verbal and nonverbal memory.

MANOVA procedures revealed a significant difference in the set of frontal-executive and verbal learning measures between those with AD who do and do not have a history of TBI, Wilks λ = .71 & .94, ps < .05, respectively. Post-hoc t-test analyses revealed those with AD who had a history of TBI performed significantly worse on WMS-IV Logical Memory I, t(116) = 2.08, p < .05, FAS, t(145) = 2.46, p < .02, Trails B, t(131) = 2.31, p < .02, and WAIS-IV Arithmetic, t(16) = 1.98, p = .05, than those without a history of TBI.

These findings suggest that a history of TBI has a negative impact on the frontal-executive and verbal learning abilities of those with AD. In particular, TBIs seem to adversely affect the verbal contextual memory, divided attention, working memory, and phonemic fluency of those with AD. These findings are likely related to the disintegrity in frontal, temporal, and white matter functioning common to TBIs, leading to a specific phenotype of cognition among those with AD and a history of TBI. Specific treatment interventions can be used to target these particular cognitive domains and their neuroanatomical and metabolic correlates, ideally following TBIs, in order to reduce their contribution to the deficits in AD. Future research can further these findings by exploring differences in cognitive profiles according to TBI severity and location.