Background Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Although many factors have been associated with increased risk of death among individuals with TBI, it is unclear to what extent they contribute to excess mortality.

Objective To quantify and describe excess mortality attributable to TBI during the 12 months after a TBI-related hospitalisation.

Methods Population-based matched cohort study using linked hospital and mortality data from four Australian states (New South Wales, Queensland, South Australia, and Tasmania). This study included individuals aged ≥18 years who were hospitalised with a principal diagnosis of TBI in 2009 (n=6,929) and a matched comparison cohort of non-injured individuals randomly selected from the electoral roll (n=6,929). The comparison group was matched 1:1 on age, sex, and postcode of residence. Survival distributions were compared using Kaplan-Meier plot with a log-rank test. Mortality rate ratios (MRR) were computed using Cox proportional hazard regression to evaluate excess mortality with and without controlling for demographic characteristics and pre-existing health status. The attributable risk percent was calculated using the adjusted MRR.