title: Population risk factor estimates for abdominal aortic aneurysm from electronic medical records: a case control study.
abstract: BACKGROUND
  Using abdominal aortic aneurysm (AAA) as a model, this case-control study used electronic medical record (EMR) data to assess known risk factors and identify new associations.
  
  
  METHODS
  The study population consisted of cases with AAA (n =888) and controls (n =10,523) from the Geisinger Health System EMR in Central and Northeastern Pennsylvania. We extracted all clinical and diagnostic data for these patients from January 2004 to December 2009 from the EMR. From this sample set, bootstrap replication procedures were used to randomly generate 2,500 iterations of data sets, each with 500 cases and 2000 controls. Estimates of risk factor effect sizes were obtained by stepwise logistic regression followed by bootstrap aggregation. Variables were ranked using the number of inclusions in iterations and P values.
  
  
  RESULTS
  The benign neoplasm diagnosis was negatively associated with AAA, a novel finding. Similarly, type 2 diabetes, diastolic blood pressure, weight and myelogenous neoplasms were negatively associated with AAA. Peripheral artery disease, smoking, age, coronary stenosis, systolic blood pressure, age, height, male sex, pulmonary disease and hypertension were associated with an increased risk for AAA.
  
  
  CONCLUSIONS
  This study utilized EMR data, retrospectively, for risk factor assessment of a complex disease. Known risk factors for AAA were replicated in magnitude and direction. A novel negative association of benign neoplasms was identified. EMRs allow researchers to rapidly and inexpensively use clinical data to expand cohort size and derive better risk estimates for AAA as well as other complex diseases.
authors.affiliation: Sigfried and Janet Weis Center for Research, Geisinger Health System, Danville, PA, USA. dtsmelser@geisinger.edu.
authors.forename: Diane T
authors.initials: DT
authors.lastname: Smelser
authors.forename: Gerard
authors.initials: G
authors.lastname: Tromp
authors.forename: James R
authors.initials: JR
authors.lastname: Elmore
authors.forename: Helena
authors.initials: H
authors.lastname: Kuivaniemi
authors.forename: David P
authors.initials: DP
authors.lastname: Franklin
authors.forename: H Lester
authors.initials: HL
authors.lastname: Kirchner
authors.forename: David J
authors.initials: DJ
authors.lastname: Carey
mesh_terms: D000367:Age Factors; D017544:Aortic Aneurysm, Abdominal / Q000209:etiology*; D016022:Case-Control Studies; D023921:Coronary Stenosis / Q000150:complications; D057286:Electronic Health Records; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications; D008171:Lung Diseases / Q000150:complications; D008297:Male; D009369:Neoplasms / Q000150:complications; D058729:Peripheral Arterial Disease / Q000150:complications; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects