Sex and Age Differences in Outcomes of Traumatic Brain Injury: Findings from the Japan Neurotrauma Data Bank

Background/Objectives: Traumatic brain injury (TBI) remains a major global health concern, contributing substantially to mortality and long-term disability. Although sex hormones have been proposed to influence TBI outcomes, sex has not been incorporated into widely used prognostic models. Given the rapidly aging population in Japan, this study aimed to investigate the impact of sex on post-TBI outcomes. Methods: We analyzed data from the Japan Neurotrauma Data Bank, comprising four prospective multicenter cohorts (P1998, P2004, P2009, P2015). Patients with Glasgow Coma Scale (GCS) scores ≥9 at admission were included. Multivariate logistic regression identified predictors of unfavorable outcomes (death, vegetative state, or severe disability) on the Glasgow Outcome Scale. Subgroup analyses stratified by sex and age were performed. Results: Of 717 eligible patients, 195 (27.2%) were females. Females were significantly older than males (median age: 68 vs. 58.5 years). Traffic accidents were more common among females, whereas non-traffic injuries predominated in males. Independent predictors of unfavorable outcomes included age ≥51 years, male sex, GCS 9-12, Injury Severity Score ≥ 16, hypoxia, targeted temperature management, and subarachnoid hemorrhage. Stratified analysis showed that females aged ≥75 years had significantly better outcomes. Conclusions: Female sex was independently associated with more favorable functional outcomes among patients with TBI presenting with admission GCS ≥ 9, particularly among those aged ≥75 years. Although prior studies have reported potential biological influences, the underlying mechanisms remain uncertain. Further investigation of sex differences and associated risk factors may help inform the development of more individualized management strategies for patients with TBI.