Impact of pre-existing co-morbidities on mortality in granulomatosis with polyangiitis: a cohort study.

Abstract

To assess the impact of pre-existing co-morbidities on mortality among patients affected by granulomatosis with polyangiitis (GPA). 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). 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)]. 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.