Introduction Despite evidence that central nervous system (CNS) trauma, including traumatic brain injury and spinal cord injury, can cause sustained neurocognitive impairment, it remains unclear whether trauma-related variables are associated with incident dementia independently of other known risk factors. Methods All adults without dementia entering the health-care system with diagnoses of CNS trauma were examined for occurrence of dementia. All trauma-related variables were examined as predictors in sex-specific Cox regression models, controlling for other known risk factors. Results Over a median follow-up of 52 months, 32,834 of 712,708 patients (4.6%) developed dementia. Traumatic brain injury severity and spinal cord injury interacted with age to influence dementia onset; women were at a greater risk of developing dementia earlier than men, all other factors being equal. Discussion Risk stratification of patients with CNS trauma by sex is vital in identifying those most likely to develop dementia and in understanding the course and modifying factors.

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Ethical approval and informed consentApproval: The study protocol was approved by the ethics committees at the clinical (Toronto Rehabilitation Institute-University Health Network) and academic (Institute for Clinical Evaluative Sciences) institutions. All methods were carried out in accordance with the relevant guidelines and regulations. Informed consent: This research utilised encrypted administrative health data with no access to personal information. Availability of materials and dataThe datasets generated during and/or analysed during the current study are available in the ICES repository, [www.ices.on.ca/ DAS