title: Epidemiology and outcome of nosocomial bloodstream infection in elderly critically ill patients: a comparison between middle-aged, old, and very old patients.
abstract: BACKGROUND
  We investigated the epidemiology of nosocomial bloodstream infection in elderly intensive care unit (ICU) patients.
  
  
  METHODS
  In a single-center, historical cohort study (1992-2006), we compared middle-aged (45-64 years; n = 524), old(65-74 years; n = 326), and very old ICU patients (> 75 years; n = 134) who developed a nosocomial bloodstream infection during their ICU stay.
  
  
  RESULTS
  Although the total number of ICU admissions (patients aged > or = 45 years) decreased by approximately 10%, the number of very old patients increased by 33% between the periods 1992-1996 and 2002-2006. The prevalence of bloodstream infection (per 1,000 ICU admissions) increased significantly over time among old (p = 0.001) and very old patients (p = 0.002), but not among middle-aged patients (p = 0.232). Yet, this trend could not be confirmed with the incidence data expressed per 1,000 patient days (p > 0.05). Among patients with bloodstream infection, the proportion of very old patients increased significantly with time from 7.2% (1992-1996) to 13.5% (1997-2001) and 17.4% (2002-2006) (p <0.001). The incidence of bloodstream infection (per 1000 patient days) decreased with age: 8.4 per thousand in middle-aged, 5.5 per thousand in old, and 4.6 per thousand in very old patients (p < 0.001). Mortality rates increased with age: 42.9%, 49.1%, and 56.0% for middle-aged, old, and very old patients, respectively (p = 0.015). Regression analysis revealed that the adjusted relationship with mortality was borderline significant for old age (hazard ratio, 1.2; 95% confidence interval, 1.0 -1.5) and significant for very old age (hazard ratio,1.8; 95% confidence interval, 1.4 -2.4).
  
  
  CONCLUSIONS
  Over the past 15 years, an increasing number of elderly patients were admitted to our ICU. The incidence of nosocomial bloodstream infection is lower among very old ICU patients when compared to middle-aged and old patients. Yet, the adverse impact of this infection is higher in very old patients.
authors.affiliation: General Internal Medicine and Infectious Diseases, Ghent University Hospital, Ghent, Belgium. stijn.blot@UGent.be
authors.forename: Stijn
authors.initials: S
authors.lastname: Blot
authors.forename: Mustafa
authors.initials: M
authors.lastname: Cankurtaran
authors.forename: Mirko
authors.initials: M
authors.lastname: Petrovic
authors.forename: Dominique
authors.initials: D
authors.lastname: Vandijck
authors.forename: Christelle
authors.initials: C
authors.lastname: Lizy
authors.forename: Johan
authors.initials: J
authors.lastname: Decruyenaere
authors.forename: Christian
authors.initials: C
authors.lastname: Danneels
authors.forename: Koenraad
authors.initials: K
authors.lastname: Vandewoude
authors.forename: Anne
authors.initials: A
authors.lastname: Piette
authors.forename: Gerda
authors.initials: G
authors.lastname: Vershraegen
authors.forename: Nele
authors.initials: N
authors.lastname: Van Den Noortgate
authors.forename: Renaat
authors.initials: R
authors.lastname: Peleman
authors.forename: Dirk
authors.initials: D
authors.lastname: Vogelaers