title: Mortality in elderly ICU patients: a cohort study.
abstract: BACKGROUND
  The population is aging. We examined changes in the proportion of elderly (≥ 80 years) intensive care unit (ICU) patients during 2005-2011 and the association between age and mortality controlling for preexisting morbidity.
  
  
  METHODS
  Through the Danish National Patient Registry, we identified a cohort of 49,938 ICU admissions (47,596 patients) in Northern Denmark from 2005 to 2011. Patients were subdivided in age groups (15-49, 50-64, 65-79 and ≥ 80 years) and calendar year. We estimated 30-day and 31-365-day mortality and mortality rate ratios (MRRs), stratified by admission type (medical and elective/acute surgical patients). Mortality was compared between age groups adjusting for sex and preexisting morbidity using 50-64-year-olds as reference.
  
  
  RESULTS
  The proportion of elderly patients increased from 11.7% of all ICU patients in 2005 to 13.8% in 2011. Among the elderly, the 30-day mortality was 43.7% in medical, 39.6% in acute surgical, and 11.6% in elective surgical ICU patients. The corresponding adjusted 30-day MRRs compared with the 50-64-year-olds were 2.7 [95% confidence interval (CI) 2.5-3.0] in medical, 2.7 (95% CI 2.4-3.0) in acute surgical, and 5.2 (95% CI 4.1-6.6) in elective surgical ICU patients. The 31-365-day mortality among elderly patients was 25.4% in medical, 26.9% in acute, and 11.9% in elective surgical ICU patients, corresponding to adjusted MRRs of 2.5 (95% CI 2.1-2.9), 2.2 (95% CI 1.9-2.5), and 1.9 (95% CI 1.6-2.3), respectively.
  
  
  CONCLUSIONS
  During 2005-2011, there was an 18% increase in the proportion of elderly ICU patients. Advancing age is associated with increased mortality even after controlling for preexisting morbidity.
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark; Department of Anaesthesia and Intensive Care Medicine, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: M S
authors.initials: MS
authors.lastname: Nielsson
authors.forename: C F
authors.initials: CF
authors.lastname: Christiansen
authors.forename: M B
authors.initials: MB
authors.lastname: Johansen
authors.forename: B S
authors.initials: BS
authors.lastname: Rasmussen
authors.forename: E
authors.initials: E
authors.lastname: Tønnesen
authors.forename: M
authors.initials: M
authors.lastname: Nørgaard
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged / Q000706:statistics & numerical data*; D000369:Aged, 80 and over; D015331:Cohort Studies; D015897:Comorbidity; D003422:Critical Care / Q000706:statistics & numerical data*; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D064266:Preexisting Condition Coverage; D006435:Renal Dialysis; D012121:Respiration, Artificial; D055815:Young Adult