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

ImportanceIncidence of traumatic brain injury (TBI) is rising in older adults. Dementia is a common comorbidity amongst older adults and may worsen post-TBI outcomes, but this has not been systematically studied. ObjectiveTo compare all-cause mortality following TBI or non-TBI trauma (NTT), and quantify the impacts of age, deprivation, and pre-injury dementia. DesignPopulation-based retrospective cohort study SettingElectronic health records (EHRs) from primary and secondary care ParticipantsAdult residents in Wales aged 18-100 with TBI or NTT from January 2000 to December 2022 ExposuresTraumatic (intracranial) brain injury (TBI) or non-TBI trauma (NTT) recorded in secondary care. Pre-injury diagnosis of dementia within primary or secondary care. Main Outcomes and MeasuresAll-cause mortality within 1, 6, and 12 months of hospitalised TBI/NTT in those with and without pre-injury dementia. Cox proportional hazard models were used to estimate survival probability across groups. Groups were propensity-matched by age, sex, and health conditions. Models were stratified by sex, age, and deprivation. Results23,428 TBIs (n=18,940) and 589,169 NTTs (n=421,259) were identified. TBIs were associated with higher mortality than NTT at all timepoints and age bands. Older age was associated with high mortality after TBI, with 16.9% of patients aged 65-79 (Hazard Ratio (HR)=4.52, 95% CI=[4.05,5.05], p<0.0001, relative to patients aged 18-39) and 31% of patients aged 80-100 dead within one month (9.08 [8.17,10.1], p<0.0001). The impact of pre-injury dementia on post-TBI mortality was specifically during the chronic phase, 6 and 12 months after injury. Using NTT without dementia as a comparator, 12-month mortality was significantly higher in TBI patients with pre-injury dementia (2.15 [2.03,2.28], p<0.0001) than those without (1.52 [1.44,1.60], p<0.0001). Conversely, 30-day mortality was significant after TBI irrespective of dementia: TBI with (2.67 [2.42, 2.95], p<0.0001) or without pre-injury dementia (2.87 [2.65, 3.12], p<0.0001) had more than twice the mortality risk relative to NTT without dementia. Conclusions and relevanceTBI is associated with higher all-cause mortality than NTT, particularly in older age. Pre-injury dementia was associated with particularly high mortality at 6 and 12 months. There is an urgent need to understand the reasons for poor outcomes in older adult TBI populations, especially those with pre-injury dementia.