Traumatic Brain Injury and Risk of Amyotrophic Lateral Sclerosis Mortality: A Traumatic Brain Injury Model Systems...

Emerging evidence suggests that amyotrophic lateral sclerosis (ALS) mortality is elevated following traumatic brain injury (TBI), reflecting a consequence of potential prodromal ALS, though the temporal patterns and underlying mechanisms remain unclear. We aimed to evaluate ALS mortality among individuals with TBI and examine temporal patterns. This study leveraged a retrospective cohort study of 20,250 individuals with complicated mild-to-severe TBI enrolled in the TBI Model Systems (TBIMS) from 1987 to 2024, with a cumulative 198,662 person-years (mean [standard deviation] = 9.8 [7.1] years) of follow-up. Standardized mortality ratios (SMRs) were calculated using the National Institute for Occupational Safety and Health Life Table Analysis System R package, adjusting for age, sex, race, and calendar year. Secondary analyses evaluated temporal patterns and injury severity differences in ALS mortality. Among 4,313 decedents in TBIMS, 11 died of ALS, representing significantly elevated mortality from ALS (SMR = 2.39; 95% confidence interval [CI]: 1.19-4.27) compared with the general population. Time-stratified analyses showed elevated ALS mortality within 2 years post-injury (SMR = 4.30; 95% CI: 1.17-11.01), but not after 2 years (SMR = 1.90; 95% CI: 0.76-3.92). Elevated ALS mortality was also observed within 2 years post-injury among those with severe TBI (SMR = 5.00; 95% CI: 1.03-14.61) and when including individuals with ALS at admission (SMR = 6.45; 95% CI: 2.37-14.04). ALS mortality was higher in the TBIMS cohort than in the general population, and this association was confined to within 2 years of injury. This pattern suggests potential reverse causality, whereby some TBIs in the cohort may have occurred in the setting of prodromal or pre-symptomatic ALS. Further investigation into TBI as a sign of subclinical ALS is warranted.