Importance Recovery after a motor vehicle crash can be slow, frustrating, and incomplete with lingering neurocognitive complications. Objective To examine whether a prior concussion is associated with increased risk of long-term disability after a motor vehicle crash. Design, Setting, and Participants This cohort study included adults surviving a motor vehicle crash treated in Ontario, Canada, from April 2003 to March 2023 with analyses to November 2025. Exposure Prior concussion. Main Outcome and Measures Long-term disability defined by official social service records, comparing those with a prior concussion and those with no history of a prior concussion. Results A total of 907 984 patients injured in a motor vehicle crash were included (mean SD age, 37 14 years; 472 435 male 52.0%); 19 851 patients had a prior concussion and 888 133 had no prior concussion. A total of 54 678 patients were subsequently diagnosed with long-term disability over 9 543 505 patient-years of follow-up (mean SD, 10.5 5.8 years), equal to an absolute risk of 1 in 17 per decade (5.7 per 1000 patient-years). Patients with a prior concussion had a 15% higher adjusted risk of long-term disability (95% CI, 9%-21%; P lt; .001) compared with those with no prior concussion. The increased risk of long-term disability was independent of other measured risk factors, applied to diverse patient groups, and included those involved as passengers or pedestrians. The increased risk extended across a spectrum of crash severity, was accentuated for single-vehicle events, replicated in analyses with artificial intelligence models adjusting for confounding, and remained distinct from the risks of death, readmission, or short-term health care costs. Conclusions and Relevance This population-based cohort study suggests a significant increased risk of long-term disability after a motor vehicle crash, particular among patients with a prior concussion. More efforts at concussion prevention and traffic safety counseling may be justified for patients.
Redelmeier et al. (Wed,) studied this question.