Background: The risk of epilepsy shortly after traumatic brain injury is high, but how long this high risk lasts is unknown. We aimed to assess the risk of epilepsy up to 10 years or longer after traumatic brain injury, taking into account sex, age, severity, and family history.
Methods: We identified 1 605 216 people born in Denmark (1977-2002) from the Civil Registration System. We obtained information on traumatic brain injury and epilepsy from the National Hospital Register and estimated relative risks (RR) with Poisson analyses.
Findings: Risk of epilepsy was increased after a mild brain injury (RR 2.22, 95% CI 2.07-2.38), severe brain injury (7.40, 6.16-8.89), and skull fracture (2.17, 1.73-2.71). The risk was increased more than 10 years after mild brain injury (1.51, 1.24-1.85), severe brain injury (4.29, 2.04-9.00), and skull fracture (2.06, 1.37-3.11). RR increased with age at mild and severe injury and was especially high among people older than 15 years of age with mild (3.51, 2.90-4.26) and severe (12.24, 8.52-17.57) injury. The risk was slightly higher in women (2.49, 2.25-2.76) than in men (2.01, 1.83-2.22). Patients with a family history of epilepsy had a notably high risk of epilepsy after mild (5.75, 4.56-7.27) and severe brain injury (10.09, 4.20-24.26).
Interpretation: The longlasting high risk of epilepsy after brain injury might provide a window for prevention of post-traumatic epilepsy.