title: Risk factors for chronic subdural haematoma formation do not account for the established male bias.
abstract: OBJECTIVE
  The 'subdural space' is an artefact of inner dural border layer disruption: it is not anatomical but always pathological. A male bias has long been accepted for chronic subdural haematomas (CSDH), and increased male frequencies of trauma and/or alcohol abuse are often cited as likely explanations: however, no study has validated this. We investigated to see which risk factors accounted for the male bias with CSDH.
  
  
  METHODS
  Retrospective review of prospectively collected data.
  
  
  RESULTS
  A male bias (M:F 97:58) for CSDH was confirmed in n=155 patients. The largest risk factor for CSDH was cerebral atrophy (M:F 94% vs. 91%): whilst a male bias prevailed in mild-moderate cases (M:F 58% vs. 41%), a female bias prevailed for severe atrophy (F:M 50% vs. 36%) (χ(2)=3.88, P=0.14). Risk factors for atrophy also demonstrated a female bias, some approached statistical significance: atrial fibrillation (P=0.05), stroke/TIA (P=0.06) and diabetes mellitus (P=0.07). There was also a trend for older age in females (F:M 72±13 years vs. 68±15 years, P=0.09). The third largest risk factor, after atrophy and trauma (i.e. anti-coagulant and anti-platelet use) was statistically significantly biased towards females (F:M 50% vs. 33%, P=0.04). No risk factor accounted for the established male bias with CSDH. In particular, a history of trauma (head injury or fall [M:F 50% vs. 57%, P=0.37]), and alcohol abuse (M:F 17% vs. 16%, P=0.89) was remarkably similar between genders.
  
  
  CONCLUSIONS
  No recognised risk factor for CSDH formation accounted for the established male bias: risk factor trends generally favoured females. In particular, and in contrast to popular belief, a male CSDH bias did not relate to increased male frequencies of trauma and/or alcohol abuse.
authors: Department of Neurosurgery, Institute of Surgery, IMB 20, PO Box 670, The Townsville Hospital, Douglas, Townsville 4810, Queensland, Australia. Electronic address: l.a.g.marshman@btinternet.com.
authors: Laurence A G
authors: LA
authors: Marshman
authors: Department of Neurosurgery, Institute of Surgery, IMB 20, PO Box 670, The Townsville Hospital, Douglas, Townsville 4810, Queensland, Australia.
authors: Appukutty
authors: A
authors: Manickam
authors: Department of Neurosurgery, Institute of Surgery, IMB 20, PO Box 670, The Townsville Hospital, Douglas, Townsville 4810, Queensland, Australia.
authors: Danielle
authors: D
authors: Carter
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000150:complications; D001284:Atrophy / Q000473:pathology; D001921:Brain / Q000473:pathology*; D006259:Craniocerebral Trauma / Q000150:complications; D048909:Diabetes Complications; D005260:Female; D020200:Hematoma, Subdural, Chronic / Q000209:etiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012737:Sex Factors
keywords: Chronic subdural haematoma; Males; Risk