title: Increased incidence of invasive bacterial disease in chronic obstructive pulmonary disease compared to the general population--a population based cohort study.
abstract: BACKGROUND
  Innate defence mechanisms of the airways are impaired in chronic obstructive pulmonary disease (COPD), predisposing patients to lower respiratory tract infections, but less is known about the association with other infections. In this population-based cohort study, we investigated the associations between COPD and invasive bacterial disease by comparing incidence rates of bacteraemia in COPD patients and randomly selected reference individuals from the general population.
  
  
  METHODS
  In this population based cohort study all patients with COPD, ≥40 years of age, who were discharged from hospitals in southern Sweden between 1990 and 2003 were identified in the Swedish Inpatient Register (n = 15,403). Age and gender matched reference individuals were randomly selected from the general population. Records were cross-referenced to the microbiological databases covering the region, 1990-2010. The hazard ratios (HR) of bloodstream infections and hospitalisations for infections were estimated by Cox proportional hazards regression.
  
  
  RESULTS
  We found that individuals with COPD had a 2.5-fold increased incidence of bacteraemia compared to the reference individuals from the general population adjusted for other co-morbidity and socio-economic status (hazard ratio: 2.5, 95% confidence interval: 2.2-2.7). The increased incidence of bacteraemia was paralleled by an increased incidence of hospitalisation for non-respiratory infections, i.e., skin infections, pyelonephritis, or septic arthritis. Despite higher absolute rates of bloodstream infections among COPD patients than among the general population, the distribution of different pathogens was similar.
  
  
  CONCLUSIONS
  In summary this population-based study shows COPD is associated with an increased incidence of invasive bacterial infections compared to the general population, indicating a general frailty of acquiring severe infections in addition to the specific susceptibility to infections of respiratory origin. The underlying contributory factors (e.g. smoking, corticosteroid use, co-morbid diseases or a frailty inherent to COPD itself) need to be disentangled in further studies.
authors.affiliation: Infection Medicine, Department of Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden. malin.inghammar@med.lu.se.
authors.forename: Malin
authors.initials: M
authors.lastname: Inghammar
authors.forename: Gunnar
authors.initials: G
authors.lastname: Engström
authors.forename: Bengt
authors.initials: B
authors.lastname: Ljungberg
authors.forename: Claes-Göran
authors.initials: CG
authors.lastname: Löfdahl
authors.forename: Adam
authors.initials: A
authors.lastname: Roth
authors.forename: Arne
authors.initials: A
authors.lastname: Egesten
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016470:Bacteremia / Q000453:epidemiology / Q000382:microbiology* / Q000473:pathology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology / Q000382:microbiology* / Q000473:pathology*; D013548:Sweden / Q000453:epidemiology