Traumatic brain injury and cognitive resilience in the Framingham Heart Study

Abstract

Background: Some evidence supports an association between traumatic brain injury (TBI) and greater risk of dementia, but the role of cognitive resilience in this association is poorly understood. Method: 2,050 participants from the Framingham Heart Study Offspring cohort who were aged ≥60 year and had a plasma total tau (t‐tau) measure at Exam 8 (2005‐2008), and a neuropsychological (NP) exam visit within five years were included. Plasma t‐tau was measured using the Simoa assay (Quanterix). NP factor scores were previously derived for memory, language, and executive function using confirmatory factor analysis. Information on TBIs was collected by comprehensive review of medical records, health history updates, exams, and self‐report. TBI occurrence and severity were operationalized using modified ACRM & VA/DoD criteria, respectively. Cognitive resilience was operationalized using a residual approach by regressing each NP factor score on the plasma t‐tau measure, adjusting for age at Exam 8, sex, education, time from blood draw, and APOE ε4 genotype. The adjusted residuals were then regressed on history of TBI (yes versus no), and severity of TBI (moderate‐to‐severe versus mild versus none). Result: The sample was, on average, 67 years of age at Exam 8, 54% female, and college educated. No differences were observed in plasma t‐tau levels between those with and without TBI. Having a history of TBI was significantly associated with a reduction in resilience in executive function (β: ‐0.110; 95% CI: ‐0.175, ‐0.044; p: 0.001) as compared to not having a history of TBI. No significant associations were observed between history of TBI and resilience in memory or language. Greater TBI severity was significantly associated with worse resilience in executive function in a dose‐response manner (Ptrend: <0.001), with the association being strongest in the moderate‐to‐severe TBI group (β: ‐0.209; 95% CI: ‐0.340, ‐0.078; p: 0.002) followed by the mild TBI group (β: ‐0.082; 95% CI: ‐0.155, ‐0.010; p: 0.026). Conclusion: Having a TBI was associated with worse resilience to neurodegeneration in executive function, and most strongly among individuals with moderate‐to‐severe TBI. These results suggest that having a TBI may increase vulnerability to late‐life executive dysfunction after accounting for a primary neurodegenerative disease process.