title: Incidence and mortality of aneurysmal subarachnoid hemorrhage in two Norwegian cohorts, 1984-2007.
abstract: OBJECTIVE
  The incidence of aneurysmal subarachnoid hemorrhage (aSAH) ranges from 4 to 10 per 100,000 person-years in most countries, and 30-day case fatality is high. The aim of this study was to estimate the incidence and case fatality of aSAH and to assess preictal predictors of survival in 2 large Norwegian population-based cohort studies.
  
  
  METHODS
  A total of 94,976 adults (≥20 years) in the Nord-Trøndelag Health Study and 31,753 participants (aged ≥20 years) in the Tromsø Study were included. During follow-up, aSAHs were identified, incidence rates were estimated, and predictors of survival were assessed using Cox and Poisson regression analysis.
  
  
  RESULTS
  A total of 214 patients with aSAH were identified during 2,077,927 person-years of follow-up from 1984 to 2007. The incidence rate was 10.3 per 100,000 person-years: 13.3 for women and 7.1 for men. The incidence increased by 2% (95% confidence interval [CI] 0-4) per 5-year time period. Case fatality at 3, 7, and 30 days was 20%, 24%, and 36%. Thirty-day case fatality remained stable during follow-up (odds ratio 1.01, 95% CI 0.97-1.06 per year). Never smokers had poorer survival after aSAH than current and former smokers combined (hazard ratio 1.6, 95% CI 0.9-2.9).
  
  
  CONCLUSIONS
  The slight increase in incidence of aSAH over time may be explained by differences in diagnostic procedures. Case fatality remained stable during 23 years of follow-up.
authors: Institutt for nevromedisin, Medisinsk teknisk forskningssenter, Trondheim, Norway. marie.s.sandvei@ntnu.no
authors: M S
authors: MS
authors: Sandvei
authors: E B
authors: EB
authors: Mathiesen
authors: L J
authors: LJ
authors: Vatten
authors: T B
authors: TB
authors: Müller
authors: H
authors: H
authors: Lindekleiv
authors: T
authors: T
authors: Ingebrigtsen
authors: I
authors: I
authors: Njølstad
authors: T
authors: T
authors: Wilsgaard
authors: M-L
authors: ML
authors: Løchen
authors: A
authors: A
authors: Vik
authors: P R
authors: PR
authors: Romundstad
mesh_terms: D000328:Adult; D000368:Aged; D003644:Death Certificates; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D012307:Risk Factors; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis* / Q000453:epidemiology* / Q000401:mortality; D055815:Young Adult