title: Nationwide trends in pneumonia hospitalization rates and mortality, Denmark 1997-2011.
abstract: OBJECTIVE
  To provide up-to-date population-based data on nationwide trends in pneumonia hospitalization rates and associated 30-day mortality.
  
  
  METHODS
  Using medical databases we identified all in-hospital episodes of pneumonia between 1997 and 2011. We computed age- and sex-standardized hospitalization rates of total and first-time pneumonia-related hospitalization and adjusted 30-day mortality rates by calendar year.
  
  
  RESULTS
  Among 552,528 pneumonia-related hospitalizations in Denmark between 1997 and 2011, 385,985 (69.9%) were first-time events. Total pneumonia hospitalizations increased by 63%, from 4.96 per 1000 population in 1997 to 8.09 in 2011. Rates of first-time pneumonia per 1000 population increased by 33%, from 3.99 in 1997 to 5.31 in 2011. Pneumonia rates stabilized in the mid-00s but primary pneumonia rates increased 16% from 2008 to 2011, most notably among children and young adults. In patients aged ≥80 years the rate of hospitalizations with secondary pneumonia more than doubled during the study period. Average 30-day mortality remained stable at 13%, but increased slightly over time in patients aged ≥80 years.
  
  
  CONCLUSIONS
  In an era of smoking cessation and vaccination efforts, pneumonia hospitalization rates are continuously increasing, largely driven by secondary diagnoses and recurrent pneumonia episodes in elderly patients. Thirty-day mortality remains persistently high.
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Olof Palmes Allé 43-45, 8200 Aarhus N, Denmark; Department of Clinical Microbiology, Aalborg University Hospital, Hobrovej 18-22, 9000 Aalborg, Denmark. Electronic address: mette.soegaard@ki.au.dk.
authors.forename: Mette
authors.initials: M
authors.lastname: Søgaard
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Olof Palmes Allé 43-45, 8200 Aarhus N, Denmark.
authors.forename: Rikke B
authors.initials: RB
authors.lastname: Nielsen
authors.affiliation: Department of Clinical Microbiology, Aalborg University Hospital, Hobrovej 18-22, 9000 Aalborg, Denmark.
authors.forename: Henrik C
authors.initials: HC
authors.lastname: Schønheyder
authors.affiliation: Department of Clinical Microbiology, Aalborg University Hospital, Hobrovej 18-22, 9000 Aalborg, Denmark.
authors.forename: Mette
authors.initials: M
authors.lastname: Nørgaard
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Olof Palmes Allé 43-45, 8200 Aarhus N, Denmark.
authors.forename: Reimar W
authors.initials: RW
authors.lastname: Thomsen
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data / Q000639:trends*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000401:mortality*; D017678:Sex Distribution; D055815:Young Adult
keywords: Age; Comorbidity; Epidemiology; Incidence; Outcome; Pneumonia