Depression Associated With APOE Status and Hippocampal Volume but Not Cognitive Decline in Older Adults Aging With Traumatic Brain Injury

Objective: To examine the relationship between depression and cognition, genetic risk, and hippocampal differences in a sample of older adults with a history of traumatic brain injury (TBI). Method: Participants were 85 males and 35 females (91 Caucasian, 29 African-American) with a mean age of 65.04 (± 8.27) years and a history of moderate, severe, or complicated mild TBI. Participants were an average of 9.33 (± 7.27) years post injury (range: 0.78–45.63). Participants underwent genetic testing, a comprehensive neuropsychological battery, surveys, and a subset underwent MRI scanning. Results: Apolipoprotein E (APOE) e4 carrier status predicted clinically significant depressive symptomatology on the Geriatric Depression Scale (GDS) with an odds ratio of 3.63, 95% CI [1.33, 9.29]. GDS was not associated with scores on measures of executive function, list learning recall, or retention. Although GDS score was initially associated with poorer confrontation naming scores and story memory recall, these effect sizes were small, and this variance was better accounted for by age and cognitive reserve. Higher GDS scores were also associated with decreased hippocampal volume. Conclusions: APOE carrier status was predictive of depression in a sample of older adults with a history of TBI. Depressive symptoms were also associated with decreased hippocampal volume but did not predict cognitive deficits in the examined domains beyond the effects of cognitive reserve. Despite the relationship between GDS and biological risks for decline, depressive symptoms in this population showed no direct relationship with cognitive decline.