Falls and Violent Mechanisms of Traumatic Brain Injury Reduce Very Long-Term Locomotor Functional Independence

Abstract

Traumatic Brain Injury (TBI) is a significant global public health concern and is a leading cause of long-term disability. In 2021, approximately 37.9 million people worldwide were living with TBI-related disabilities (Liu et al., 2026). While research on short-term post-TBI outcomes is well documented, much less is known about how TBI mechanisms shape functional independence across the lifespan. As such, the objective of this dissertation was to determine whether TBI mechanisms predict very long-term locomotor and stair-climbing functional abilities post-TBI. The dissertation comprises three separate investigations. The first involved a systematic review synthesizing existing research on the relationship between TBI mechanisms and long-term functional independence outcomes. In accordance with PRISMA standards, studies were identified, screened, and evaluated for risk of bias to clarify how TBI mechanisms from falls, motor vehicle accidents (MVAs), violence-related injuries, and sports-related injuries affect long-term functional recovery trajectories. Findings from different studies commonly indicate strong evidence that TBI mechanisms are associated with variability in long-term functional outcomes and disability. Secondly, a longitudinal analysis examined whether TBI mechanisms predict very long-term locomotor functional independence. Data were obtained from the Traumatic Brain Injury Model Systems (TBIMS) national database. Ordinal Functional Independence Measure (FIM) locomotion scores were converted to interval-level logit measures via Rasch analysis, thereby enhancing measurement accuracy and interpretability. After converting the data, linear mixed-effects regression models were applied to evaluate locomotor functional trajectories across follow-up data collections (collected up to 30 years post-TBI). Third, there is another longitudinal analysis focusing on a more complex mobility activity requiring coordination, balance, and lower-body strength: stair-climbing for functional independence. Using the same Rasch analysis procedure and subsequent mixed-effects modeling, longitudinal changes in stair-climbing ability were examined over 30 years post-TBI. In both longitudinal analyses, TBI mechanisms were significant predictors of the respective mobility-related functional independence domains. Individuals with TBIs caused by either falls or violence-related mechanisms exhibited lower very long-term locomotor and stair-climbing functional independence relative to their peers with TBIs from MVAs or sports-related mechanisms. The results indicate that TBI mechanisms function as an early prognostic indicator of very long-term functional recovery. Collectively, this dissertation highlights the longitudinal impact of injury mechanism on mobility trajectories post-TBI and emphasizes the necessity of integrating etiological context into long-term rehabilitation planning. By synthesizing a systematic review with longitudinal mixed-effects modeling using Rasch-transformed functional measures, this work expands current knowledge of how TBI mechanisms shape functional independence decades post-TBI and provides evidence to support clinical prognostication and rehabilitation strategy development.