title: Impact of pre-existing co-morbidities on mortality in granulomatosis with polyangiitis: a cohort study.
abstract: OBJECTIVE
  To assess the impact of pre-existing co-morbidities on mortality among patients affected by granulomatosis with polyangiitis (GPA).
  
  
  METHODS
  By means of the Danish National Hospital Register, we identified a cohort of patients hospitalized for GPA during 1994-2010 (n = 308). The burden of pre-existing co-morbidities among the patients was quantified according to the Charlson Comorbidity Index (CCI). Each patient was matched with five age- and gender-matched population controls with no pre-existing co-morbidities captured by the CCI (CCI score = 0). The study subjects were followed throughout 2010. Cox regression analyses were used to calculate mortality rate ratios (MRRs).
  
  
  RESULTS
  The median duration of follow-up in the GPA cohort was 5.8 years (interquartile range 2.3-10.0). Compared with their matched population controls, the MRR for patients presenting with a CCI score of 0 (n = 246) was 3.9 (95% CI 2.0, 7.5) during years 0-2 and 1.4 (95% CI 0.9, 2.0) from the second year of follow-up onwards. The corresponding MRRs were 13.3 (95% CI 5.8, 31) and 1.9 (95% CI 1.1, 3.6) for patients with a CCI score ⩾1 (n = 62). In a direct comparison, GPA patients with a CCI score ⩾1 were found to have significantly higher mortality than GPA patients with a CCI score of 0 during years 0-2 [adjusted MRR 3.4 (95% CI 1.6, 7.0)] but not after >2 years of follow-up [adjusted MRR 1.3 (95% CI 0.7, 2.6)].
  
  
  CONCLUSIONS
  During early follow-up periods, the mortality among GPA patients with pre-existing co-morbidities is markedly higher than that among GPA patients with no pre-existing illnesses. Our analyses identify an increased CCI score for pre-existing co-morbidities as an important risk factor for a fatal outcome in GPA.
authors.affiliation: Department of Rheumatology, and mikkelf@dadlnet.dk.
authors.forename: Mikkel
authors.initials: M
authors.lastname: Faurschou
authors.affiliation: Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Magnus G
authors.initials: MG
authors.lastname: Ahlström
authors.affiliation: Department of Rheumatology, and.
authors.forename: Jesper
authors.initials: J
authors.lastname: Lindhardsen
authors.affiliation: Department of Rheumatology, and.
authors.forename: Bo
authors.initials: B
authors.lastname: Baslund
authors.affiliation: Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Obel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D015897:Comorbidity; D003718:Denmark / Q000453:epidemiology; D005260:Female; D014890:Granulomatosis with Polyangiitis / Q000401:mortality*; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D012042:Registries; D012720:Severity of Illness Index; D055815:Young Adult
keywords: Charlson; co-morbidity; granulomatosis with polyangiitis; mortality; vasculitis