title: Recurrence of Subdural Haematoma in a Population-Based Cohort - Risks and Predictive Factors.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Linnea
authors.initials: L
authors.lastname: Schmidt
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Sanne
authors.initials: S
authors.lastname: Gørtz
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Jan
authors.initials: J
authors.lastname: Wohlfahrt
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Mads
authors.initials: M
authors.lastname: Melbye
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark; Department of Neurosurgery, Copenhagen University Hospital, Denmark.
authors.forename: Tina Noergaard
authors.initials: TN
authors.lastname: Munch
mesh_terms: D000328:Adult; D000368:Aged; D003920:Diabetes Mellitus / Q000453:epidemiology; D005260:Female; D006408:Hematoma, Subdural / Q000453:epidemiology* / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000706:statistics & numerical data; D012008:Recurrence; D014947:Wounds and Injuries / Q000453:epidemiology