title: Reporting on statistical methods to adjust for confounding: a cross-sectional survey.
abstract: BACKGROUND
  The use of complex statistical models to adjust for confounding is common in medical research.
  
  
  OBJECTIVE
  To determine the frequency and adequacy of adjustment for confounding in medical articles.
  
  
  METHODS
  Cross-sectional survey.
  
  
  METHODS
  34 scientific medical journals with a high impact factor.
  
  
  METHODS
  Frequency of reporting on methods used to adjust for confounding in 537 original research articles published in January 1998.
  
  
  RESULTS
  Of the 537 articles, 169 specified that adjustment for confounding was used. In 1 paper in 10, it was unclear which statistical method was used or for which variables adjustment was made. In 45% of papers, it was not clear how multicategory or continuous variables were treated in the analysis. Inadequate reporting was less frequent if an author was affiliated with a department of statistics, epidemiology, or public health and if articles were published in journals with a high impact factor.
  
  
  CONCLUSIONS
  Details of methods used to adjust for confounding are frequently not reported in original research articles.
authors.affiliation: Universitätsklinik für Notfallmedizin, Allgemeines Krankenhaus Wien, Währinger Gürtel 18-20/6D, A-1090 Vienna, Austria. marcus.muellner@univie.ac.at.
authors.forename: Marcus
authors.initials: M
authors.lastname: Müllner
authors.forename: Hugh
authors.initials: H
authors.lastname: Matthews
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Altman
mesh_terms: D015986:Confounding Factors, Epidemiologic; D003430:Cross-Sectional Studies; D006801:Humans; D010506:Periodicals as Topic / Q000592:standards; D016032:Randomized Controlled Trials as Topic / Q000592:standards; D012107:Research Design / Q000592:standards*; D013223:Statistics as Topic / Q000592:standards*