title: Impact of smoking cessation on the risk of subarachnoid haemorrhage: a nationwide multicentre case control study.
abstract: OBJECTIVE
  Subarachnoid haemorrhage (SAH) is the most devastating cerebrovascular disease. Cigarette smoking is one of the established risk factors for SAH, but the risk of SAH has not been properly elucidated in relation to smoking cessation.
  
  
  METHODS
  We performed a nationwide multicentre case control study involving 33 hospitals in Korea. A total of 426 SAH cases and 426 age and sex matched controls were enrolled. We obtained detailed information on lifestyle, medical history and, in particular, smoking habits from participants using structured questionnaires.
  
  
  RESULTS
  148 SAH patients (37.4%) were current smokers compared with 103 (24.2%) controls, giving an adjusted OR of 2.84 (95% CI, 1.63 to 4.97) after controlling for possible confounders. Based on cumulative dose of smoking (pack years), the risk of SAH was found to increase in a dose-responsive fashion. Smoking cessation (≥5 years) caused a reduction in SAH to 59% (p<0.05). However, participants with a history of heavy smoking (≥20 cigarettes per day) had a 2.3 times increased risk of SAH compared with participants who had never smoked (p<0.05).
  
  
  CONCLUSIONS
  We have demonstrated that cigarette smoking increases the risk of SAH, but smoking cessation decreases the risk in a time dependent manner, although this beneficial effect may be diminished in previous heavy smokers. To forestall tragic SAH events, our results call for more global and vigorous efforts for people to stop smoking.
authors.affiliation: Department of Neurology, Seoul National University Hospital, 28 Yeongeon-dong, Jongno-gu, Seoul 110-744, Republic of Korea.
authors.forename: Chi Kyung
authors.initials: CK
authors.lastname: Kim
authors.forename: Beom Joon
authors.initials: BJ
authors.lastname: Kim
authors.forename: Wi-Sun
authors.initials: WS
authors.lastname: Ryu
authors.forename: Seung-Hoon
authors.initials: SH
authors.lastname: Lee
authors.forename: Byung-Woo
authors.initials: BW
authors.lastname: Yoon
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D016540:Smoking Cessation / Q000706:statistics & numerical data*; D013345:Subarachnoid Hemorrhage / Q000453:epidemiology* / Q000209:etiology