title: Eighteen-year trends in stroke mortality and the prognostic influence of comorbidity.
abstract: OBJECTIVE
  To examine 18-year trends in short-term and long-term stroke mortality and the prognostic influence of comorbidity.
  
  
  METHODS
  We conducted a nationwide population-based cohort study. Using the Danish National Registry of Patients, covering all Danish hospitals, we identified all 219,354 patients with a first-time hospitalization for stroke during 1994-2011. We computed standardized 30-day, 1-year, and 5-year mortality by sex. Comorbidity categories were defined by Charlson Comorbidity Index scores of 0 (none), 1 (moderate), 2 (severe), and 3 or more (very severe). Calendar periods of diagnosis (1994-1998, 1999-2003, 2004-2008, and 2009-2011) and comorbidity categories were compared by means of mortality rate ratios based on Cox regression.
  
  
  RESULTS
  Over time, the 30-day mortality rate ratio adjusted for age, sex, and comorbidity decreased by approximately 45% for ischemic stroke (standardized risk decreased from 17.2% in 1994-1998 to 10.6% in 2009-2011) and by 35% for intracerebral hemorrhage (from 43.2% to 33.8%). The absolute mortality reduction occurred for all levels of comorbidity. Five-year mortality risk decreased from 56.4% in 1994-1998 to 46.1% in 2004-2008 for ischemic stroke and from 66.1% to 61.0% for intracerebral hemorrhage. Comparing very severe comorbidity with no comorbidity, 30-day and 5-year mortality rate ratios were both approximately 2.5-fold increased for ischemic stroke and 1.7-fold increased for intracerebral hemorrhage.
  
  
  CONCLUSIONS
  Short- and long-term mortality improved considerably between 1994 and 2011 for all types of stroke. Short-term mortality improved regardless of comorbidity burden. However, comorbidity burden was a strong prognostic factor for both short- and long-term mortality.
authors.affiliation: From the Departments of Clinical Epidemiology (M.S., J.B.J., S.P.J., H.T.S.) and Cardiology (M.S., H.E.B.), Aarhus University Hospital, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Schmidt
authors.forename: Jacob B
authors.initials: JB
authors.lastname: Jacobsen
authors.forename: Søren P
authors.initials: SP
authors.lastname: Johnsen
authors.forename: Hans E
authors.initials: HE
authors.lastname: Bøtker
authors.forename: Henrik T
authors.initials: HT
authors.lastname: Sørensen
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D018672:Community Health Planning; D015897:Comorbidity; D003704:Dementia / Q000453:epidemiology; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006331:Heart Diseases / Q000453:epidemiology / Q000401:mortality; D006801:Humans; D007674:Kidney Diseases / Q000453:epidemiology / Q000401:mortality; D008107:Liver Diseases / Q000453:epidemiology / Q000401:mortality; D008171:Lung Diseases / Q000453:epidemiology / Q000401:mortality; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models; D012307:Risk Factors; D020521:Stroke / Q000453:epidemiology* / Q000401:mortality*; D013997:Time Factors; D055815:Young Adult