Recurrence of Subdural Haematoma in a Population-Based Cohort – Risks and Predictive Factors

OBJECTIVES To estimate the risks of and identify predictors for recurrent subdural haematoma in surgically and conservatively treated patients. METHODS The cohort comprised all individuals diagnosed with a first-time subdural hematoma in Denmark 1996-2011. Information on potential predictors was retrieved from the Danish health registers. Cumulative recurrence risks were estimated using the Aalen-Johansen estimator. Rate ratios (RR) were estimated using Poisson regression. RESULTS Among 10,158 individuals with a subdural hematoma, 1,555 had a recurrent event. The cumulative risk of recurrent subdural hematoma was 9% at 4 weeks after the primary bleeding, increasing to and stabilising at 14% after one year. Predictors associated with recurrence were: Male sex (RR 1.60, 95% CI:1.43-1.80), older age (>70 years compared to 20-49 years; RR 1.41, 95% CI: 1.21-1.65), alcohol addiction (RR 1.20, 95% CI:1.04-1.37), surgical treatment (RR 1.76, 95% CI:1.58-1.96), trauma diagnoses (RR 1.14, 95% CI:1.03-1.27), and diabetes mellitus (RR 1.40, 95% CI:1.11-1.74). Out of a selected combination of risk factors, the highest cumulative 1-year recurrence risks for subdural hematoma of 25% (compared to 14% for all patients) was found in surgically treated males with diabetes mellitus. CONCLUSIONS The recurrence risk of subdural hematoma is largely limited to the first year. Patient characteristics including co-morbidities greatly influence the recurrence risk of SDH, suggesting that individualized prognostic guidance and follow-up is needed.