Apathy, or loss of motivation and interest, is a common sequela of moderate to severe traumatic brain injury (msTBI) and has been associated with frontal lesions and with executive dysfunction in a sample an average of one year post injury (Andersson & Bergdalen, 2002). In older adults sustaining msTBI in particular, the appearance of apathy is more likely to be comorbid with depression when compared to injury in younger adults (Kant et al., 1998). However, studies have consistently shown an important dissociation between apathy and depression, despite overlapping symptoms, with apathy in particular associated with frontal lobe damage (Worthington & Wood, 2018). The present study holds two primary goals. First, to examine the relationship between current apathy ratings and cognition after controlling for ratings of depression and perceived changes in apathy, to account for the unique relationship of injury-related apathy on cognition. Second, to examine the potential variable role of APOE4 carrier status on depression and apathy ratings.

110 older adults with a lifetime history of msTBI (M=9.5 years post-injury) were included as part of a cross-sectional study. Apathy was measured using the Frontal Systems and Behaviors Scale (FrSBe) for both current apathy ratings and perceived change in apathy from pre- to post-injury. Depression was measured using the depression subscale of the Brief Symptom Inventory (BSI). Outcome measures included normed scores for learning (HVLT-R total recall), retention (HVLT-R percent retention), processing speed (Trails A), set-shifting and working memory (Trails B, Digit Span Backwards), and phonemic and category fluency (D-KEFS letter and category fluency). The main independent variable of interest was current apathy ratings. Depression and perceived apathy change were included as control variables for all analyses. Vif scores were calculated for all analyses to ensure that variables were not multicollinear. Finally, we ran an ANOVA to examine the relationship between apathy, depression, and APOE4 carrier status.

When controlling for depression and perceived changes in apathy, current apathy ratings were associated with poorer performance on learning (p=.04, n2=.04), processing speed (p=.001, n2=.10), set-shifting (p=.02, n2=.05), attention (p=.04, n2=.04), phonemic fluency (p=.001, n2=.09), category fluency (p=.001, n2=.10). Current apathy ratings were not associated with retention or working memory. Apathy was significantly associated with depression (p <.001), but was not associated with APOE4 carrier status or the interaction between depression and carrier status.

Despite overlap between depressive symptoms and apathy questionnaires (i.e., loss of interest/pleasure), by controlling for depressive symptoms and perceived changes following injury, we demonstrate the significant independent association of apathy and cognition in an older sample with chronic msTBI. Further, although previous work has shown strong associations between depression and APOE4 carrier status in chronic msTBI samples (Vervoordt et al., 2021), there was no significant relation with apathy directly in our sample, providing further evidence that these are neurobiologically distinct syndromes.