Intracranial hemorrhage after head injury among older patients on anticoagulation seen in the emergency department: a population-based cohort study

BACKGROUND: Intracranial hemorrhage (ICH) after head injury is a concern among older adult patients on anticoagulation. We evaluated the risk of ICH after an emergency department visit for head injury among patients 65 years and older taking warfarin or a direct oral anticoagulant (DOAC) compared with patients not taking anticoagulants. We also evaluated risk of 30-day mortality and neurosurgical intervention among patients with ICH. METHODS: In this retrospective cohort study, we used population-based data of patients 65 years and older seen in an Ontario emergency department with a head injury. We matched patients on the propensity score to create 3 pairwise-matched cohorts based on anticoagulation status (warfarin v. DOAC, warfarin v. no anticoagulant, DOAC v. no anticoagulant). For each cohort, we calculated the relative risk of ICH at the index emergency department visit and 30-day mortality. We also calculated the hazard of neurosurgical intervention among patients with ICH. RESULTS: We identified 77 834 patients with head injury, including 64 917 (83.4%) who were not on anticoagulation, 9214 (11.8%) who were on DOACs and 3703 (4.8%) who were on warfarin. Of these, 5.9% of patients had ICH at the index emergency department visit. Patients on warfarin had an increased risk of ICH compared with matched patients on DOACs (relative risk [RR] 1.43, 95% confidence interval [CI] 1.20-1.69) and patients not on anticoagulation (RR 1.36, 95% CI 1.15-1.61). We did not observe a difference in ICH between patients on DOACs compared with matched patients not on anticoagulation. In patients with ICH, 30-day mortality did not differ by anticoagulation status or type. Patients on warfarin had an increased hazard of neurosurgery compared with patients not on anticoagulation. INTERPRETATION: Patients on warfarin seen in the emergency department with a head injury had higher relative risks of ICH than matched patients on a DOAC and patients not on anticoagulation, respectively. The risk of ICH for patients on a DOAC was not significantly different compared with no anticoagulation. Further research should confirm that older adults using warfarin are the only group at higher risk of ICH after head injury.