title: Directed acyclic graphs helped to identify confounding in the association of disability and electrocardiographic findings: results from the KORA-Age study.
abstract: OBJECTIVE
  To examine the association between electrocardiographic (ECG) findings and disability status in older adults.
  
  
  METHODS
  KORA-Age, a population-based cross-sectional study of the MONICA/KORA project, a randomized sample from Southern Germany of people aged 65 years or older.
  
  
  RESULTS
  A total of 534 (51.5%) of 1,037 participants were characterized as disabled. Disabled participants were on average 4.5 years older than those who were not disabled. Crude associations of left-axis deviation, ventricular conduction defects, atrial fibrillation, and QT prolongation with disability status were significant (P < 0.05). In models controlled for age and sex, these effects remained constant except for QT prolongation. In the models adjusted for the minimal sufficient adjustment set (consisting of the variables sex, physical activity, age, obesity, diabetes, education, heart diseases, income, lung diseases, and stroke) identified by a directed acyclic graph (DAG), no significant association could be shown.
  
  
  CONCLUSIONS
  Associations between specific ECG findings and disability were found in unadjusted analysis and logistic models adjusted for age and sex. However, when adjusting for other possible confounders identified by the DAG, all these associations were no longer significant. It is important to adequately identify confounding in such settings.
authors.affiliation: Institute for Medical Information Processing, Biometrics and Epidemiology, Ludwig-Maximilians-Universität München, Marchioninistraße 17, 81377 Munich, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Röhrig
authors.affiliation: Institute for Medical Information Processing, Biometrics and Epidemiology, Ludwig-Maximilians-Universität München, Marchioninistraße 17, 81377 Munich, Germany. Electronic address: ralf.strobl@med.uni-muenchen.de.
authors.forename: Ralf
authors.initials: R
authors.lastname: Strobl
authors.affiliation: Institute for Medical Information Processing, Biometrics and Epidemiology, Ludwig-Maximilians-Universität München, Marchioninistraße 17, 81377 Munich, Germany; German Center for Vertigo and Balance Disorders, Ludwig-Maximilians-Universität MÃ1/4nchen, Marchioninistraβe 15, 81377 Munich, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Müller
authors.affiliation: Institute for Biological and Medical Imaging, Helmholtz-Zentrum München, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany.
authors.forename: Siegfried
authors.initials: S
authors.lastname: Perz
authors.affiliation: Department of Medicine I, Klinikum Grosshadern, Ludwig-Maximilians-Universität München, Marchioninistraβe 15, 81377 Munich, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Kääb
authors.affiliation: Department of Medicine I, Klinikum Grosshadern, Ludwig-Maximilians-Universität München, Marchioninistraβe 15, 81377 Munich, Germany.
authors.forename: Eimo
authors.initials: E
authors.lastname: Martens
authors.affiliation: Institute of Epidemiology II, Helmholtz-Zentrum München, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany.
authors.forename: Annette
authors.initials: A
authors.lastname: Peters
authors.affiliation: Institute of Epidemiology II, Helmholtz-Zentrum München, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Linkohr
authors.affiliation: Institute for Medical Information Processing, Biometrics and Epidemiology, Ludwig-Maximilians-Universität München, Marchioninistraße 17, 81377 Munich, Germany; German Center for Vertigo and Balance Disorders, Ludwig-Maximilians-Universität MÃ1/4nchen, Marchioninistraβe 15, 81377 Munich, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Grill
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac; D053840:Brugada Syndrome; D000075224:Cardiac Conduction System Disease; D003430:Cross-Sectional Studies; D006233:Persons with Disabilities / Q000706:statistics & numerical data*; D004562:Electrocardiography / Q000706:statistics & numerical data*; D005260:Female; D005858:Germany / Q000453:epidemiology; D006329:Heart Conduction System / Q000002:abnormalities; D006331:Heart Diseases / Q000453:epidemiology*; D006801:Humans; D016015:Logistic Models; D008297:Male
keywords: Aged; Cross-sectional study; Directed acyclic graph (DAG); Disability evaluation; ECG abnormalities; Electrocardiography