title: Comorbidity and its change predict survival in incident dialysis patients.
abstract: BACKGROUND
  Few studies have performed a comprehensive comparison of the prognostic importance of comorbidity to that of other case-mix factors influencing incident dialysis patients' survival. Longitudinal change in the comorbid illness burden of incident dialysis patients has not been measured. Comorbidity severity and its change may serve as important prognostic markers of survival, independent of other case-mix factors.
  
  
  METHODS
  The Choices for Healthy Outcomes in Caring for End-Stage Renal Disease Cohort Study used the Index of Coexistent Disease (ICED) to assess comorbidity at the initiation of chronic dialysis treatment (1,039 incident patients) and during follow-up (733 patients). Using proportional hazards regression analyses, the relationship to survival of baseline ICED level and change in ICED level was examined.
  
  
  RESULTS
  At the initiation of chronic dialysis treatment, 36% of patients were at ICED level 0 to 1 (least comorbidity severity); 35%, level 2; and 29%, level 3. After multivariable adjustment, baseline ICED level was the strongest predictor of subsequent mortality. Compared with ICED level 0 to 1, relative risks for mortality were 1.9 (95% confidence interval, 1.3 to 2.6) for ICED level 2 and 2.8 (95% confidence interval, 2.0 to 3.9) for ICED level 3. The prevalence and severity of most comorbid conditions increased during follow-up. After controlling for baseline ICED level and other factors, change in ICED level over time was significantly associated with mortality (P = 0.01).
  
  
  CONCLUSIONS
  Indexing comorbidity when patients begin chronic dialysis therapy and recording the evolution of index scores yields a predictor of mortality risk that is independent of other case-mix factors.
authors.affiliation: Division of Nephrology, Tufts-New England Medical Center, Boston, MA 02111, USA. dmiskulin@lifespan.org
authors.forename: Dana C
authors.initials: DC
authors.lastname: Miskulin
authors.forename: Klemens B
authors.initials: KB
authors.lastname: Meyer
authors.forename: Alice A
authors.initials: AA
authors.lastname: Martin
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Fink
authors.forename: Josef
authors.initials: J
authors.lastname: Coresh
authors.forename: Neil R
authors.initials: NR
authors.lastname: Powe
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Klag
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Levey
mesh_terms: D015331:Cohort Studies; D015897:Comorbidity; D005260:Female; D005500:Follow-Up Studies; D006305:Health Status Indicators; D006801:Humans; D015994:Incidence; D007676:Kidney Failure, Chronic / Q000453:epidemiology* / Q000401:mortality / Q000628:therapy; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010530:Peritoneal Dialysis / Q000379:methods / Q000401:mortality*; D015995:Prevalence; D006435:Renal Dialysis / Q000379:methods / Q000401:mortality*; D018570:Risk Assessment; D012720:Severity of Illness Index; D012959:Socioeconomic Factors; D015996:Survival Rate; D013997:Time Factors