Accelerated Aging after Traumatic Brain Injury: An ENIGMA Multi‐Cohort Mega‐Analysis

Objective The long‐term consequences of traumatic brain injury (TBI) on brain structure remain uncertain. Given evidence that a single significant brain injury event increases the risk of dementia, brain‐age estimation could provide a novel and efficient indexing of the long‐term consequences of TBI. Brain‐age procedures use predictive modeling to calculate brain‐age scores for an individual using structural magnetic resonance imaging (MRI) data. Complicated mild, moderate, and severe TBI (cmsTBI) is associated with a higher predicted age difference (PAD), but the progression of PAD over time remains unclear. We sought to examine whether PAD increases as a function of time since injury (TSI) and if injury severity and sex interacted to influence this progression. Methods Through the ENIGMA Adult Moderate and Severe (AMS)‐TBI working group, we examine the largest TBI sample to date (n = 343), along with controls, for a total sample size of n = 540, to replicate and extend prior findings in the study of TBI brain age. Cross‐sectional T1w‐MRI data were aggregated across 7 cohorts, and brain age was established using a similar brain age algorithm to prior work in TBI. Results Findings show that PAD widens with longer TSI, and there was evidence for differences between sexes in PAD, with men showing more advanced brain age. We did not find strong evidence supporting a link between PAD and cognitive performance. Interpretation This work provides evidence that changes in brain structure after cmsTBI are dynamic, with an initial period of change, followed by relative stability in brain morphometry, eventually leading to further changes in the decades after a single cmsTBI. ANN NEUROL 2024;96:365–377