Traumatic brain injury and mortality in older adults with and without pre-injury dementia

BACKGROUND: Incidence of traumatic brain injury (TBI) is rising in older adults. Dementia is a common comorbidity and may worsen post-TBI outcomes, but its effects have not been studied. OBJECTIVE: To compare all-cause mortality following TBI or non-TBI trauma (NTT) and quantify the impacts of age, deprivation and dementia. DESIGN: Population-based retrospective cohort study. SETTING: Linked primary and secondary care electronic health records from the Secure Anonymised Information Linkage Databank. SUBJECTS: Adult residents in Wales aged 18-100 with hospitalised TBI or NTT recorded between January 2000 and December 2022. METHODS: Cox proportional hazard models were used to estimate survival within 1, 6 and 12 months of hospitalised TBI/NTT in those with and without pre-injury dementia diagnosis. Groups were propensity-matched by age, sex and morbidities. Models were stratified by age, sex and deprivation. RESULTS: A total of 23 428 TBIs (n = 18 940) and 589 169 NTTs (n = 421 259) were identified. TBIs were associated with higher mortality than NTT at all timepoints. Older age was associated with higher mortality after TBI, with 16.9% 1-month mortality in patients aged 65-79, and 31% in patients aged 80-100. In TBI patients, 30-day mortality was significant irrespective of dementia. About 6- and 12-month mortality were higher in those with than without pre-injury dementia diagnosis. CONCLUSIONS: TBI is associated with higher all-cause mortality than NTT, particularly in older age. Among those with TBI, patients with pre-injury dementia had particularly high chronic mortality. There is an urgent need to understand the reasons for poor outcomes in older adult TBI populations, especially those with dementia.