title: The contribution of longitudinal comorbidity measurements to survival analysis.
abstract: BACKGROUND
  Many clinical and health services research studies are longitudinal, raising questions about how best to use an individual's comorbidity measurements over time to predict survival.
  
  
  OBJECTIVE
  To evaluate the performance of different approaches to longitudinal comorbidity measurement in predicting survival, and to examine strategies for addressing the inevitable issue of missing data.
  
  
  METHODS
  Retrospective cohort study using Cox regression analysis to examine the association between various Romano-Charlson comorbidity measures and survival.
  
  
  METHODS
  Fifty thousand cancer-free individuals aged 66 or older enrolled in Medicare between 1991 and 1999 for at least 1 year.
  
  
  RESULTS
  The best fitting model combined both time independent baseline comorbidity and the time dependent prior year comorbidity measure. The worst fitting model included baseline comorbidity only. Overall, the models fit best when using the "rolling" comorbidity measures that assumed chronic conditions persisted rather than measures using only prior year's recorded diagnoses.
  
  
  CONCLUSIONS
  Longitudinal comorbidity is an important predictor of survival, and investigators should make use of individuals' longitudinal comorbidity data in their regression modeling.
authors.affiliation: Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave North, Seattle, WA 98109, USA. cywang@fhcrc.org
authors.forename: C Y
authors.initials: CY
authors.lastname: Wang
authors.forename: Laura-Mae
authors.initials: LM
authors.lastname: Baldwin
authors.forename: Barry G
authors.initials: BG
authors.lastname: Saver
authors.forename: Sharon A
authors.initials: SA
authors.lastname: Dobie
authors.forename: Pamela K
authors.initials: PK
authors.lastname: Green
authors.forename: Yong
authors.initials: Y
authors.lastname: Cai
authors.forename: Carrie N
authors.initials: CN
authors.lastname: Klabunde
mesh_terms: D000368:Aged; D002423:Cause of Death; D015897:Comorbidity; D003625:Data Collection / Q000379:methods; D003627:Data Interpretation, Statistical; D005260:Female; D015577:Geriatric Assessment; D006302:Health Services Research / Q000379:methods* / Q000592:standards; D006304:Health Status; D006305:Health Status Indicators; D006801:Humans; D016013:Likelihood Functions; D008137:Longitudinal Studies; D008297:Male; D006278:Medicare / Q000706:statistics & numerical data; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D012107:Research Design; D012189:Retrospective Studies; D018426:SEER Program; D016019:Survival Analysis; D013997:Time Factors; D014481:United States / Q000453:epidemiology