title: Beyond comorbidity: expanding the definition and measurement of complexity among older adults using administrative claims data.
abstract: BACKGROUND
  Studies of patients with multiple chronic conditions using claims data are often missing important determinants of treatments and outcomes, such as function status and disease severity. We sought to identify and evaluate a class of function-related indicators (FRIs) from administrative claims data.
  
  
  METHODS
  The study cohort comprised US Medicare beneficiaries aged 65 years or older with Parts A and B fee-for-service and Part D coverage, with a hospitalization for acute myocardial infarction during 2007.
  
  
  METHODS
  Measures during the year before admission included the FRIs, demographics, conventional comorbidity measures, and prior hospitalization. Outcomes were receipt of cardiac catheterization during the index hospitalization and 12-month mortality. Model development used a random sample (n=72,056) with an equal sample for validation.
  
  
  RESULTS
  In addition to prior cardiovascular conditions (85%), 40% had ≥1 comorbid condition, 30% were hospitalized in the prior 6 months, and 65% had ≥1 FRI [eg, delirium/dementia (22.7%), depression (16.7%), mobility limitation (16.1%), and chronic skin ulcers (12.6%)]. Including the FRIs improved mortality and cardiac catheterization prediction models (C-statistics 0.71 and 0.77, respectively). Patients with more cardiovascular conditions received less cardiac catheterization [minimally adjusted odds ratio (OR) 0.83; 95% confidence interval (CI), 0.82-0.83], as did patients with more comorbidities (minimally adjusted OR 0.70; 95% CI, 0.69-0.71), but this was attenuated by adjusting for functional status (fully adjusted OR for cardiovascular conditions 0.95; 95% CI, 0.94-0.96 and for comorbid conditions 0.94; 95% CI, 0.92-0.95).
  
  
  CONCLUSIONS
  Claims data studies that include indicators of potentially diminished patient functional status better capture heterogeneity of patients with multiple chronic conditions.
authors.affiliation: *Department of Epidemiology, The University of Iowa College of Public Health, Iowa City †Schneider Research Associates LLC ‡Buccaneer, a General Dynamics Company, Des Moines, IA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Chrischilles
authors.forename: Kathleen
authors.initials: K
authors.lastname: Schneider
authors.forename: June
authors.initials: J
authors.lastname: Wilwert
authors.forename: Gregory
authors.initials: G
authors.lastname: Lessman
authors.forename: Brian
authors.initials: B
authors.lastname: O'Donnell
authors.forename: Brian
authors.initials: B
authors.lastname: Gryzlak
authors.forename: Kara
authors.initials: K
authors.lastname: Wright
authors.forename: Robert
authors.initials: R
authors.lastname: Wallace
mesh_terms: D000368:Aged; D002318:Cardiovascular Diseases / Q000453:epidemiology / Q000628:therapy; D002908:Chronic Disease / Q000145:classification* / Q000453:epidemiology / Q000628:therapy*; D015331:Cohort Studies; D015897:Comorbidity; D016001:Confidence Intervals; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology / Q000628:therapy; D005260:Female; D006801:Humans; D007345:Insurance Claim Review / Q000706:statistics & numerical data*; D007674:Kidney Diseases / Q000453:epidemiology / Q000628:therapy; D016015:Logistic Models; D008297:Male; D006278:Medicare / Q000706:statistics & numerical data*; D001523:Mental Disorders / Q000453:epidemiology / Q000628:therapy; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D012720:Severity of Illness Index; D014481:United States / Q000453:epidemiology